Also k nown as th Inter natio al Electr otech ical Voca ular y IE o ln... 13 B.1 In e div dis harg s in olvin in ulatin s ld materials.. 13 B.2.2 Calc late maximum safe flow v lo itie f
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Trang 3Edition 1.1 2 17-0
Explosiv e atmospher es –
Part 3 -1: Ele trostatic hazards, guidanc
Trang 61 Sc p 14
2 Normativ refere c s 14
3 Terms an d finitio s 17
4 Nome clature 2
5 Ge eral 21
6 Static ele tricity in s l d materials 2
6.1 Ge eral c n id ratio s 2
6.2 Th u e of c n u tiv or dis ipativ materials in plac of in ulatin o e 2
6.2.1 Ge eral c n id ratio s 2
6.2.2 Dis ipativ s ld materials 2
6.2.3 Earthin of c n u tiv an dis ipativ items 2
6.3 Pre autio s re uire wh n u in in ulatin s ld materials 2
6.3.1 Ge eral 2
6.3.2 Re trictio s o th siz of c arg able in ulatin s rfac s 2
6.3.3 Earth d metal me h s 2
6.3.4 In ulatin c atin s o earth d c n u tiv s rfac s 2
6.3.5 Co d ctiv or dis ipativ c atin s o in ulatin materials 2
6.3.6 Static dis ipativ ag nts 3
6.3.7 Humidificatio 3
6.3.8 Io isatio / Charg Ne tral satio 3
6.3.9 Meth d to d termin th in e divity of dis harg s 31
6.4 Co v y r b lts an tran mis io b lts 3
6.4.1 Ge eral 3
6.4.2 Co v y r b lts 3
6.4.3 Tran mis io b lts 3
7 Static ele tricity in lq id 3
7.1 Ge eral c n id ratio s 3
7.1.1 Oc ur e c of flammable atmo p ere 3
7.1.2 Ig itio s n itivity an lmitatio s to th s o e of ad ic 3
7.1.3 Chargin me hanisms 3
7.1.4 Charg ac umulatio an c n u tivity clas ificatio s 3
7.1.5 In e div dis harg s pro u e d rin l q id han ln o eratio s 3
7.2 Summary of pre autio s again t ig itio hazard d rin lq id han l n o eratio s 3
7.2.1 Earthin an av idan e of is late c n u tors 3
7.2.2 Re trictin c arg g n ratio 3
7.2.3 Av idan e of a flammable atmo p ere 3
7.2.4 Promotin c arg dis ipatio 3
7.3 T n s an Co tain rs 3
7.3.1 Ge eral 3
7.3.2 Co d ctiv tan s an c ntain rs 4
7.3.3 T n s an c ntain rs mad e tirely of dis ipativ material 5
Trang 77.6 Gau in an sampln in tan s 6
7.6.1 Ge eral 6
7.6.2 Pre autio s d rin gau in an sampl n 6
7.7 Pip s an h s as embl e for l q id 61
7.7.1 Ge eral 61
7.7.2 Pip s 61
7.7.3 Ho e an h s as embl e 6
7.8 Sp cial fi in pro e ure 7
7.8.1 Aircraf fu l n 7
7.8.2 Road tan er d l v rie 71
7.8.3 Retai fi in statio s 7
7.8.4 Mo i e or temp rary l q id han ln e uipme t 7
7.9 Plant pro e s s (ble din , stir in , mixin , cry tal satio an stir e reactors) 7
7.9.1 Ge eral 7
7.9.2 Earthin 7
7.9.3 In-l n ble din 7
7.9.4 Ble din in v s els or tan s 7
7.9.5 Jet mixin 7
7.9.6 Hig s e d mixin 7
7.10 Sprayin l q id an tan cleanin 7
7.10.1 Ge eral 7
7.10.2 T n cleanin with low or me ium pre s re water jets (u to ab ut 12 bar) 7
7.10.3 T n cleanin with low c n u tivity l q id 7
7.10.4 T n cleanin with hig pre s re water or s lv nt jets (ab v 12 bar) 7
7.10.5 Steam cleanin tan s 7
7.10.6 Water d lu e s stems 8
7.1 Glas s stems 8
7.1 1 Ge eral 8
7.1 2 Pre autio s to b tak n for low c n u tivity l q id 8
8 Static ele tricity in gas s 81
8.1 Ge eral 81
8.2 Grit blastin 81
8.3 Fire e tin uis ers 8
8.4 In rtin 8
8.5 Steam cleanin 8
8.6 Ac id ntal leakag of c mpre s d gas 8
8.7 Sprayin of flammable paints an p wd rs 8
8.7.1 Ge eral 8
8.7.2 Earthin 8
8.7.3 Plastic s ray cabin ts 8
Trang 89.1 Ge eral 8
9.2 Dis harg s, o c r e c an in e divity 8
9.3 Pro e ural meas re 8
9.3.1 Ge eral 8
9.3.2 Humidificatio 8
9.3.3 Ho e for p e matic tran fer 8
9.3.4 Io isatio 8
9.4 Bulk materials in th ab e c of flammable gas s an vap urs 8
9.4.1 Ge eral 8
9.4.2 Eq ipme t an o je ts mad of c n u tiv or dis ipativ materials 8
9.4.3 Eq ipme t an o je ts mad of in ulatin materials 8
9.4.4 Du t s parators 8
9.4.5 Sio an Co tain rs 8
9.5 Ad itio al re uireme ts for b lk material in th pre e c of flammable gas s an vap urs 9
9.5.1 Ge eral 9
9.5.2 Meas re for re istivity greater e ual 10 MΩ m 9
9.5.3 Meas re for re istivity le s than 10 MΩ m 9
9.5.4 Fi in of b lk material into a c ntain r 9
9.6 Fle ible interme iate b lk c ntain rs (FIBC) 9
9.6.1 Ge eral 9
9.6.2 Ad itio al pre autio s wh n u in FIBC 9
10 Static ele tricity wh n han l n e plo iv s an ele tro-e plo iv d vic s 9
10.1 Ex lo iv s man facture, han l n an storag 9
10.1.1 Ge eral 9
10.1.2 First d gre prote tio 9
10.1.3 Interme iate prote tio 9
10.1.4 Se o d d gre prote tio 9
10.2 Han l n of ele tro-e plo iv d vic s 10
10.2.1 Ge eral 10
10.2.2 Earthin 10
10.2.3 Pre autio s d rin storag an is u 101
10.2.4 Pre autio s d rin pre aratio for u e 101
1 Static ele tricity o p o le 101
1 1 Ge eral c n id ratio s 101
1 2 Static dis ipativ flo rs 10
1 3 Dis ipativ an c n u tiv fo twear 10
1 4 Su pleme tary d vic s for earthin of p o le 10
1 5 Clothin 10
1 6 Glo e 10
1 7 Oth r Items 10
12 Ele tro tatic s o k 10
Trang 913.2.2 Practical criteria 1 0
13.3 Earthin re uireme ts in practical s stems 1 2
13.3.1 Al-metal s stems 1 2
13.3.2 Metal plant with in ulatin parts 1 3
13.3.3 In ulatin materials 1 4
13.3.4 Co d ctiv an dis ipativ materials 1 5
13.3.5 Earthin via intrin ic safety circ its 1 5
An e A (informativ ) Fu dame tals of static ele tricity 121
A.1 Ele tro tatic c argin 121
A.1.1 Intro u tio 121
A.1.2 Co tact c argin 121
A.1.3 Co tact c argin of lq id 121
A.1.4 Charg g n ratio o lq id flowin in pip s 12
A.1.5 Charg g n ratio in fiters 12
A.1.6 Charg g n ratio d rin stir in an mixin of lq id 12
A.1.7 Setl n p te tials 12
Trang 10A.3.1 Intro u tio 12
A.3.2 Spark 12
A.3.3 Coro a 13
A.3.4 Bru h dis harg s 13
A.3.5 Pro agatin bru h dis harg s 131
A.3.6 Lig tnin l k dis harg s 131
A.3.7 Co e dis harg s 13
A.4 Meas reme ts for ris as e sme t 13
An e B (informativ ) Ele tro tatic dis harg s in s e ific situatio s 13
B.1 In e div dis harg s in olvin in ulatin s ld materials 13
B.1.1 Ge eral 13
B.1.3 Bru h dis harg s from in ulatin s l d materials 13
B.1.4 Pro agatin bru h dis harg s from in ulatin s l d materials 13
B.2 In e div dis harg s pro u e d rin l q id han ln 13
B.2.1 Ge eral 13
B.2.2 Calc late maximum safe flow v lo itie for fi in me ium
-siz d v rtical axis storag tan s 13
B.3 In e div dis harg s pro u e d rin p wd r han l n an storag 13
B.3.6 Spark dis harg s in p wd r pro e s s 13
B.3.7 Bru h dis harg s in p wd r pro e s s 13
B.3.8 Coro a dis harg s in p wd r pro e s s 13
B.3.9 Pro agatin bru h dis harg s in p wd r pro e s s 13
An e C (informativ ) Flammabi ty pro ertie of s b tan e 14
Trang 12G.9.4 Te t sample 16
G.9.5 Pro e ure for mo eable items 16
G.9.6 Pro e ure for in tal e items 161
Fig re 4 – Difere c b twe n earthin an b n in 10
Fig re 5 – Hazard u earth d c n u tor in c ntact with a flowin in ulator 1 4
Fig re A.1 – Eq ivale t ele trical circ it for an ele tro tatical y c arg d c n u tor 12
Trang 13Fig re G.3 – Meas rin c l for lq id c n u tivity 15
Fig re G.4 – Ig itio pro e 16
Fig re G.5 – Perforate plate of ig itio pro e 16
Fig re G.6 – Example of an ar an eme t for meas reme t of c arg d cay 17
Fig re G.7 – Ele tro e for meas rin breakthro g v ltag of s e ts 17
T ble 1 – Bo n ary lmits at (2 ± 2) °C an (2 ± 5) % RH for th c aracterisatio of
s ld materials an e ample for th clas ificatio of o je ts 2
T ble 2 – Maximum alowe is late capacitan e in Zo e with e plo iv atmo p ere 2
T ble 3 – Re trictio o siz of in ulatin s ld materials in hazard u areas 2
T ble 4 – Maximum ac e table tran fer e c arg 3
T ble 5 – Re uireme ts for c n e or b lts 3
T ble 6 – Re uireme ts for tran mis io b lts 3
T ble 7 – Co d ctivitie an relaxatio time of s me lq id 3
T ble 8 – Pre autio s for fi in larg c n u tiv tan s with low c n u tivity l q id 4
T ble 9 – Fi in rate l mits for fi in me ium-siz d v rtical-axis tan s thro g s h d le 4 pip s 4
T ble 10 – Velo ity an fi in rate l mits for loadin low c n u tivity lq id into s ort (N=1), fix d h riz ntal axis tan s via s h d le 4 pip s 4
T ble 1 – Ve icle an c mpartme ts s itable for hig -s e d loadin for ADR c mplant v hicle 5
T ble 12 – Influ n e of th s lp ur c nte t o mid le disti ate v lmits for road tan ers 51
T ble 13 – Velo ity an fi in rate l mits for road tan ers bas d o s h d le 4 pip s; rate for h s s wi b simiar 51
T ble 14 – Velo ity an fi in rate l mits for loadin rai tan ers 5
T ble 15 – Clas ificatio of e d- o-e d h s re istan e for c ntrol of hazard from static ele tricity an stray c r e t 6
T ble 16 – ISO 8 31 clas ificatio of h s grad s 6
T ble 17 – Hy rid grad s of h s s an h s as emble 6
T ble 18 – Ho e s le tio T ble for flammable l q id s rvic 6
T ble 19 – Us of th difere t ty e of FIBC 9
T ble 2 – In er l n rs an FIBC: c mbinatio s that are p rmis ible an n t p rmis ible in hazard u atmo p ere 9
T ble 21 – Determinatio of re uireme t for ele tro tatic dis ipativ prote tiv clothin
an oth r items of p rs nal prote tiv e uipme t 10
T ble 2 – Summary of maximum earthin re istan e for th c ntrol of static
ele tricity in hazard u areas 1 1
T ble A.1 – Charg b i d u o p wd rs 12
Trang 15EXPLOSIVE ATMOSPHERES –
Part 32-1: Electrostatic hazards, guidance
FOREWORD
1) Th Intern tio al Electrotech ical Commis io (IEC) is a worldwid org nizatio for sta d rdizatio comprisin
al n tio al electrotech ical commite s (IEC Natio al Commite s) Th o ject of IEC is to promote
intern tio al co-o eratio o al q estio s co cernin sta d rdizatio in th electrical a d electro ic fields To
this e d a d in a ditio to oth r activities, IEC p blsh s Intern tio al Sta d rds, Tech ical Sp cificatio s,
Tech ical Re orts, Pu lcly Av ia le Sp cificatio s (P S) a d Guid s (h re fer refere to as “IEC
Pu lcatio (s) Th ir pre aratio is e truste to tech ical commite s; a y IEC Natio al Commite intereste
in th su ject d alt with may p rticip te in this pre aratory work Intern tio al g v rnme tal a d n
n-g v rnme tal org nizatio s laisin with th IEC also p rticip te in this pre aratio IEC cola orates closely
with th Intern tio al Org nizatio for Sta d rdizatio (ISO) in ac ord nce with co ditio s d termin d by
a re me t b twe n th two org nizatio s
2) Th formal d cisio s or a re me ts of IEC o tech ical maters expres , as n arly as p s ible, a intern tio al
co se sus of o inio o th rele a t su jects since e ch tech ical commite h s re rese tatio from al
intereste IEC Natio al Commite s
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th later
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oth r d ma e of a y n ture wh tso v r, wh th r direct or in irect, or for costs (inclu in le al fe s) a d
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in isp nsa le for th corect a plcatio of this p blcatio
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p te t rig ts IEC sh l n t b h ld resp nsible for id ntifyin a y or al such p te t rig ts
DISCLAIMER
This Consol dated versio is n t an of icial IEC Standard an ha be n prepared for
us r co venienc Only the cur ent versions of the stan ard an its amendment s)
are to be co sidered the of icial d cuments
This Co sol dated versio of IEC TS 6 079-3 -1 be rs the edition n mber 1.1 It
co sists of the first editio (2 13-0 ) [d cuments 31/10 3/DTS an 31/1076/RVC] an its
amen ment 1 (2 17-0 ) [documents 31/12 7/DT and 31/12 3/RVC] The te h ic l
co tent is identic l to the ba e edition an its amen ment
In this Redl ne version, a vertic l l ne in the margin sh ws where the te h ic l co tent
is mo ified by amen ment 1 Ad itio s are in gre n text, deletions are in strikethro gh
red text A s parate Final versio with al change a c pted is avai able in this
p bl c tion
Trang 16• th s bje t is sti u d r te h ical d v lo me t or wh re, for an oth r reas n, th re is th
future b t n imme iate p s ibi ty of an agre me t o an Internatio al Stan ard
Te h ical s e ificatio s are s bje t to re iew within thre y ars of p blcatio to d cid
wh th r th y can b tran forme into Internatio al Stan ard
IEC/TS 6 0 9-3 -1, whic is a te h ical s e ificatio , has b e pre are b IEC Te h ical
Commite 31: Eq ipme t for e plo iv atmo p ere , an IEC Te h ical Commite 101:
Ele tro tatic
This p blcatio has b e drafe in ac ordan e with th ISO/IEC Dire tiv s, Part 2
A lst of al parts of th IEC 6 0 9 s rie , u d r th g n ral title Ex lo sive atmosp he re s, can
b fo n o th IEC we site
Th c mmite has d cid d that th c nte ts of th bas p blcatio an its ame dme t wi
"htp:/we store.ie c " in th data relate to th s e ific p blcatio At this date, th
IMPORTANT – The 'colo r inside' log o the cover page of this p bl c tio in ic te
that it contains colours which are co sidered to be us ful for the cor e t
u derstandin of its contents Us rs sh uld therefore print this d cument usin a
colo r printer
A bi n ual v rsio of this p blcatio may b is u d at a later date
Trang 17• from German : TRBS 215 :2 0 , Preve ting risks ofignitio due to ele ctrostatic c arges,
• from Sh l Internatio al Petrole m: Static ele ctric ity – Te h ic l a d safety aspe c ts,
• from th US: NFPA 7 , R e comme nde d Prac tic o Static Ele ctricity (2 0 7),
• from Japan: JNIOSH TR4 , R e comme datio ns for Requ ireme ts fo r Avo iding Ele c trostatic
Ha ards in Industry (20 0 7),
• from ASTM, EUROPIA, IEC, Internatio al c amb r of s ip in , ISO etc
It giv s th b st avai able ac e te state of th art g idan e for th av idan e of hazard d e
to static ele tricity
This d c me t is mainly write for d sig ers an u ers of pro e s s an e uipme t,
man facturers an te t h u e It can als b u e b s p l ers of e uipme t (e.g mac in s)
an flo rin or ap arel wh n n pro u t famiy or d dicate pro u t stan ard e ists or wh re
th e istin stan ard d e n t d al with ele tro tatic hazard
A s c n part, IEC 6 0 9-3 -2, Electro static Ha ards, Te sts, is u d r d v lo me t
Trang 181 Scope
This part of IEC 6 0 9 giv s g idan e ab ut th e uipme t, pro u t an pro e s pro ertie
n c s ary to av id ig itio an ele tro tatic s o k hazard arisin from static ele tricity as
wel as th o eratio al re uireme ts n e e to e s re safe u e of th e uipme t, pro u t or
pro e s It can b u e in a ris as e sme t of ele tro tatic hazard or for th pre aratio of
pro u t fami y or d dicate pro u t stan ard for ele trical or n n-ele trical mac in s or
e uipme t
Th hazard as o iate with static ele tricity in in u trial pro e s s an e viro me ts that
mo t c mmo ly giv pro lems are c n id re Th s pro e s s in lu e th han ln of
s ld , lq id , p wd rs, gas s, s ray an e plo iv s In eac cas , th s urc an nature of
th ele tro tatic hazard are id ntifie an s e ific re omme datio s are giv n for d aln with
th m
Th p rp s of this d c me t is to pro id stan ard re omme datio s for th c ntrol of static
ele tricity, s c as earthin of c n u tors, re u tio of c argin an re trictio of c arg able
areas of in ulators In s me cas s static ele tricity play an inte ral part of a pro e s, e.g
ele tro tatic c atin , b t ofe it is an u welc me sid efe t an it is with th lat er that this
g idan e is c n ern d If th stan ard re omme datio s giv n in this d c me t are fulfi e it
can b e p cte that th ris of hazard u ele tro tatic dis harg s in an e plo iv
atmo p ere is at an ac e tably low le el
If th re uireme ts of this d c me t can ot b fulfi e , alternativ ap roac e can b ap l e
u d r th c n itio that at least th same le el of safety is ac ie e
Basic informatio ab ut th g n ratio of u d sirable static ele tricity in s l d , lq id ,
gas s, e plo iv s, an als o p o le, to eth r with d s riptio s of h w th c arg s
IEC/TR 613 0-1
This Te h ical Sp cificatio is n t ap l cable to th hazard of static ele tricity relatin to
lg tnin or to damag to ele tro ic c mp n nts
This Te h ical Sp cificatio is n t inte d d to s p rs d stan ard that c v r s e ific
pro u ts an in u trial situatio s
2 Normative referenc s
Th folowin d c me ts, in wh le or in part, are n rmativ ly refere c d in this d c me t an
are in is e sable for its ap lcatio For date refere c s, o ly th e itio cite ap le For
ame dme ts) ap l e
IEC 6 0 9-0:2 1 , Ex losive atmo sp ere s – Part 0: Equ ipme t – Ge ne ral re qu ire me ts
IEC 6 0 9-10-1, Ex lo sive atmosp he res – Part 10-1: C las ificatio n o f are s – Exp losive gas
atmosp e re s
Trang 19IEC 6 0 9-2 -1, Exp lo sive atmo sp e res – Part 2 -1: Mate rial c ara teristics fo r g as a d
va our c las ific atio n – Te st meth ds a d data
IEC 6 0 9-3 -2
1
:2 15, Ex lo sive atmo sp ere s – Part 32-2: Ele c tro static h z rds – Te sts
IEC 6 0 3, Meth ods of te st fo r volume re sistivity a d surfac e re sistivity o f sold ele ctric al
insu lating mate rials
IEC 6 16 , Meth ds of te st fo r th dete rmin tio of th insu latio resista c e of sold
insu lating materials
IEC 613 0-2-3, Ele c trostatics – Part 2-3: Me th ds o f te st fo r dete rmining th re sista c e a d
re sistivity ofsold pla ar mate rials used to avoid ele ctrostatic c arg e a cu mu latio
IEC 613 0-4-1, Ele tro statics – Part 4-1: Sta dard test me tho ds fo r sp cific a plc atio s –
Ele c tric al re sistan c e offlo or c o ve rings a d instale d floo rs
IEC 613 0-4-3, Ele tro statics – Part 4-3: Sta dard test me tho ds fo r sp cific a plc atio s –
Foo twe r
IEC 613 0-4-4:2 12, Ele tro statics – Part 4-4: Sta dard te st meth ds fo rsp e cific a p licatio s
– Ele tro static clas ific tio n of fle xib le inte rmediate b ulk containe rs (FIBC)
ISO 2 4, Co ve yo r belts – Ele ctrical c o nductivity – Sp e c ific tio a d te st meth d
ISO 6 9 , Petroleum p ro ducts – Aviatio a d disti ate fu e ls – De termin tio o f ele ctric al
co nductivity
ISO 8 31, Ru bb e r a d plastics ho se s a d ho se as e mb lie s – De termin tio of ele trical
re sista c e
ISO 9 6 , Belt drive s; ele ctric al conductivity of a tistatic e dle ss sy c hro nous be lts;
c arac teristics a d te st meth d
ISO 1210 -1, Safety o f mac hine ry – Basic c ncepts, ge e ral p rinc iple s fo r de sign – Part 1:
Basic te rmin logy, me th dology
ISO 16 9 , Tyre s – Ele tric al re sista c – Te st me tho d fo r me suring ele c trical re sista ce of
tyres o a te st rig
ISO 21 7 , Light conve yor be lts – De te rmin tio o f ele ctrical re sista ce s
ISO 21 7 , Lig ht c o nve o r b elts – De termin tio of th ele c trostatic field g e nerated by a
running lght c o nve yo r b elt
ISO 21 8 -1, Light conve yo r b elts – Part 1: Princ ip al c ara te ristics a d ap plc atio ns
—————————
Trang 20ASTM D4 0 -9 , Sta dard Te st Meth d fo r Ele c tric al C onductivity o fLiqu id Hydro c arb ons by
Pre c isio Mete r
ASTM E5 2-8 , Sta dard te st meth d for minimu m ignitio e ergy a d qu e nching dista c e in
gase us mixture s
ASTM E2 19-0 , Sta dard te st me tho d for minimum ignitio e e rgy of a dust clou d in air
ASTM F15 , Sta dard Test Me tho d fo r Electric l R e sista c of C onduc tive a d Static
Dis ip tive Resi e t Flo ring
ASTM F19 1, Sta dard Te st Meth d fo r Ele c tric al Resista c e of Tire s Unde r L ad On th
Te st Be nc h
BS 5 5 : Code o f prac tic e fo r contro l o f u nde sira le static ele c tricity
Part 1: Ge e ral c nside ratio ns
Part 2: R e comme datio s fo r p rticu lar industrial situ atio ns
BS 7 0 , Meth ds fo r me sureme nts in electro statics – Part 2 Te st me tho ds
DIN 51412-1, Te sting of pe trole u m p ro ducts; de te rmin tio of th ele c tric al c o nductivity,
lab o ratory me tho d
DIN 51412-2, Te sting of p etro leu m p roduc ts; de termin tio of th ele ctrical c o nductivity; field
meth d
EN 10 1, R e si e t flo or c ve rings – De termin tio o f th ele c tric l re sista c
EN 1 4 -3, Pro te cting clo the s – Ele c tro static p rop e rtie s – Part 3: Test meth d for me suring
th c harg e dis ip atio
EN 1 4 -5, Protective c lothing – Ele c tro static p ro pe rties – Part 5: Material p ero rma c e a d
de sig n requ ireme ts
EN 13 0, Rub b er a d plastic ho se s a d ho se as emb lie s fo r me sured fu el disp nsing
systems – Sp cific atio n
EN 13 1, R u bb er ho se s a d h se as emb lie s for aviatio fuel h ndlng – Sp e c ific tio
EN 13 6 -1, No -e le c tric l equipme t fo r p te tialy flamma le atmo sp ere s – Part 1: Basic
principle s a d ge neral requ ireme ts
EN 1412 , Undergrou nd pip work fo r p trol fi ing statio s
EN 14 7 , C o nve o r belts fo r use in u nde rgrou nd instalatio s – Ele tric al a d flammab ilty
safe ty re qu ire me ts
Inte rn tio nal Safe ty Guide fo r Oi Ta ke rs a d Termin ls (ISGOTT), fifh e itio , Internatio al
c amb r of s ip in , 2 0
Trang 21© IEC 2 17
JNIOSH TR 4 , Rec mme datio s fo r Requ ireme ts fo r Avoiding Ele c trostatic Ha ards in
Industry
NFPA 7 , R e comme nde d p ra tice o static ele ctricity
SAE J16 5, Su rfa e ve icle re comme nde d p ra tice – Fuel systems a d C o mpo ne ts –
Ele c tro static Charge Mitigatio
3 Terms and definitions
For th p rp s s of this d c me t th folowin terms an d finitio s ap ly:
3.1
antistatic
c n u tiv or dis ipativ
Note 1 to e try: Use to d s rib a material th t is inca a le of retainin a sig ifica t electrostatic ch rg wh n
in co tact with e rth In this co text th word is commo ly use to d s rib a typ of fo twe r a d a tistatic
a ditiv s (A As) for use with lq ids
Note 2 to e try: Prefere term is co d ctiv or dis ip tiv d p n in o which is corect
3.2
co d ctive
havin a re istivity or re istan e b low th dis ipativ ran e (s e 3.7) al owin stray c r e t
arc an ele tro tatic s o k to o c r
Note 1 to e try: Co d ctiv materials or o jects are n ith r dis ip tiv n r insulatin a d are inca a le of
retainin a sig ifica t electrostatic ch rg wh n in co tact with e rth
Note 2 to e try: Bo n ary lmits for th co d ctiv ra g are giv n for sold materials, e closures a d some
o jects in 6.1 (Ta le 1), a d for b lk materials in 9.1 For certain items, sp cial d finitio s are maintain d in oth r
sta d rds (se 3.3, 3.8 a d 3.9)
Note 3 to e try: Pro uct sta d rds a d oth r sta d rds co erin electrostatic pro erties ofe inclu e sp cific
d finitio s of “co d ctiv ” which a ply o ly to items co ere by th se sta d rds a d may b difere t to th
d finitio s giv n h re Se e.g ISO 8 31 a d ISO 8 3 for h se a d h se as embles
3.3
co d ctive fo twe r
fo twear e s rin that a p rs n stan in o a c n u tiv flo r has a re istan e to earth low
e o g to e s re dis ipatio of ele tro tatic c arg s e e in partic larly hazard u situatio s
(e.g wh n han ln s n itiv e plo iv s) b t n t hig e o g to pre e t a hazard u
ele trical s o k at v ltag s le s than 5 0 V
Trang 22Note 1 to e try: Dis ip tiv materials or o jects are n ith r co d ctiv n r insulatin b t, lk co d ctiv items,
safely lmit co tact ch rgin a d/or dis ip te e e th maximum ch rgin cure ts as ociate with th ir d sig e
a plcatio wh n in co tact with e rth
Note 2 to e try: Bo n ary lmits for th dis ip tiv ra g are giv n for sold materials, e closures a d some
o jects in Ta le 1, a d for b lk materials in 9.1 For certain items, sp cial d finitio s are maintain d in oth r
sta d rds (se 3.3, 3.8 a d 3.9)
Note 3 to e try: Pro uct sta d rds ofe inclu e sp cific d finitio s of “dis ip tiv ” which a ply o ly to items
co ere by th se sta d rds a d may b difere t to th d finitio sgiv n h re
3.8
dis ipative clothin
clothin that me ts th material an d sig re uireme ts s e ifie in EN 1 4 -5
3.9
dis ipative footwe r
fo twear e s rin that a p rs n stan in o a c n u tiv or dis ipativ flo r has a re istan e
to earth low e o g to e s re dis ipatio of ele tro tatic c arg s b t hig e o g to pre e t
a hazard u ele trical s o k at v ltag s le s than 5 0 V
area in whic flammable or e plo iv gas/vap ur-air or d st air mixture or aero ols are, or
can b , pre e t in s c q antitie as to re uire s e ial pre autio s again t ig itio
Note 1 to e try: Se IEC 6 0 9-10-1a d IEC 6 0 9-10-2 A sh rt summary is giv n in An ex D
3.13
high chargin
a pro e s that g n rate a hig er rate of ele tro tatic c argin than simple man al
o eratio s
E AMPLE Ru bin , cle nin with a cloth, raisin from a se t, walkin , wipin of cloth s etc
Note 1 to e try: Typical examples of hig ch rgin o eratio s inclu e e.g th flow of insulatin lq ids or
p wd rs a d hig v lta e spray ch rgin
Trang 23© IEC 2 17
3.14
h brid mixture
an e plo ible h tero e e u mixture, c mprisin gas or vap ur with s s e d d partic late
s ld or l q id, in whic th total flammable gas c n e tratio is at least 10 % of its lower
flammable lmit (L L) an th total s s e d d partic late c n e tratio is at least 10 % of its
minimum e plo ible c n e tratio (MEC)
3.15
insulatin
havin a re istivity or re istan e that is hig er than th dis ipativ ran e (s e 3.7)
Note 1 to e try: Insulatin materials or o jects are n ith r co d ctiv n r dis ip tiv Electrostatic ch rg s ca
ac umulate o th m a d d n t re diy dis ip te e e wh n th y are in co tact with e rth
Note 2 to e try: Bo n ary lmits for th insulatin ra g are giv n for sold materials, e closures a d some
o jects in Ta le 1, for b lk materials in 9.1 For certain items, sp cial d finitio s are maintain d in oth r sta d rds
(se 3.3, 3.8 a d 3.9)
Note 3 to e try: Pro uct sta d rds a d oth r sta d rds co erin electrostatic pro erties ofe inclu e sp cific
d finitio s of “insulatin ” which a ply o ly to items co ere by th se sta d rds a d may b difere t to th
d finitio s giv n h re Se e.g ISO 8 31 a d ISO 8 3 for h se a d h se as embles
Note 4 to e try: Th a jectiv “n n-co d ctiv ” h s ofe b e use as a s n nym for insulatin It is a oid d in
this d cume t as it co ld b ta e to me n eith r “insulatin ” or “insulatin or dis ip tiv ” a d this may le d to
Note 1 to e try: Th resista ce d p n s u o th v lume or surface resistivity of th materials a d th dista ce
b twe n th ch se p int of me sureme t a d e rth
Note 2 to e try: On commo co fig ratio (e.g in IEC 613 0-4-1, ISO 10 6 a d A TM F15 ) uses a circular
electro e, (6 ± ) mmin diameter
3.18
minimum ig itio energ
MIE
minimum e erg that can ig ite a mixture of a s e ifie flammable material with air or o y e ,
meas re b a stan ard pro e ure
Note 1 to e try: Se A TM E5 2-8 for g ses a d v p urs, IEC 612 1-2-3, A TM E2 19-0 a d E 13 21 for
relaxatio time
time d rin whic th ele tro tatic c arg o a s l d s rfac or in th b lk of a lq id or
p wd r d cay e p n ntial y to 1/e (i.e ab ut 3 %) of its original valu (s e A.2.2)
Trang 24Note 2 to e try: Th surface resista ce is d p n e t u o th electro e co fig ratio Th surface resista ce
me sure with th example electro e co fig ratio is te times lower th n th surface resistivity
Note 3 to e try: Sof co d ctiv ru b r strip electro es are prefere o er siv r p int electro es
3.2
surfa e re istivity
re istan e acro s o p site sid s of a s rfac of u it le gth an u it width c mmo ly
e pre s d in o ms (or o ms/s uare)
Note 1 to e try: This co fig ratio is use e.g in A TM D2 7 a d B 7 0 -2
3.2
v lume re istivity
re istan e of a b d of u it le gth an u it cro s-s ctio al area e pre s d in o m metre
4 Nomenclature
Ele tro tatic safety re ulatio s u e man adje tiv s to clas ify th c n u tin abi ty of
materials an o je ts Difere t re ulatio s an dif ere t in u trie u e difere t adje tiv s
an , e e wh n th same adje tiv s are u e , th ir d finitio s can vary Th n me clature
that is s stematical y folowe in this d c me t is giv n h re in ord r to av id c nfu io an
to as ist with tran latio :
Sol d materials are clas ifie as c n u tiv , dis ipativ or in ulatin ac ordin to th ir
v lume re istivity (s e 3.2, 3.7 an 3.15) Bo n ary l mits are giv n in Table 1
Sol d obje ts an texti e are clas ifie as c n u tiv , dis ipativ or in ulatin ac ordin to
th ir s rfac or leakag re istan e, d p n in o ap lcatio (s e 3.2, 3.7 an 3.15)
Bo n ary lmits for e clo ure an s me o je ts are giv n in Table 1 For c rtain items,
s e ial d finitio s are maintain d in oth r stan ard (s e 3.3, 3.8 an 3.9)
Bulk materials (p wders etc.) are clas ifie as low, me ium or hig re istivity ac ordin to
th ir v lume re istivity (s e 9.1 for b u dary lmits)
Liquids are clas ifie as hig , me ium or low c n u tivity ac ordin to th ir ele trical
c n u tivity (s e 7.1.4 for b u dary lmits)
NOT More d tais a o t electrostatic pro erties, co ce ts a d termsare giv n in An exesAto G
Re istanc s hav mainly b e state in e p n ntial form in oth r d c me ts Howe er,
e p n nts are smal fig re , an th e p n nts 6, 8 an 9 mainly u e in ele tro tatic are
easi y misread in printe or proje te d c me ts, an e e u readable if th y o c r in n te
For this reas n this d c me t u e SI prefix s in tead of e p n nts:
103
Ω = 1 kΩ
106
Ω = 1 MΩ
108
Ω = 10 MΩ
Trang 25© IEC 2 17
109
Ω = 1 GΩ
101
A = 1 mA
10-6
A = 1 µA
10-9
A = 1 nA
10-12
A = 1 pA
Static ele tricity o c rs c mmo ly in in u try an dai y lfe Man of th efe ts are harmle s
an eith r pas c mpletely u n tic d or are simply a n isan e, b t static ele tricity can als
giv ris to a hazard u situatio In s c situatio s, th hazard can g n ral y b re u e b
c arg relaxatio (s e An e A)
Hazard cau e b ele tro tatic c arg in lu e:
a) ig itio an / or e plo io of flammable atmo p ere , s e IEC 6 0 9-0 an EN 13 6 -1;
b) ele tro tatic s o k in c mbinatio with an th r hazard (e.g fal, trip) − s e ISO 1210 -1;
c) ele tro tatic s o k givin ris to injury or d ath, s e ISO 1210 -1;
d) damag to ele tro ic (n t c v re b this d c me t
In ad itio , static ele tricity can intro u e o eratio al pro lems d rin man facturin an
han ln pro e s s, e.g b cau in article to ad ere to eac oth r, or b atractin d st
Static ele tricity is g n rate b :
a) th c ntact an s paratio of s ld e.g th mo eme t of c n e or b lts, plastic fi m,
etc o er rolers, th mo eme t of a p rs n;
b) th flow of l q id or p wd rs, an th pro u tio of s ray ;
c) in u tio p e ome a, i.e o je ts reac hig p te tial or b c me c arg d d e to b in in
an ele tric field
Th ac umulatio of ele tro tatic c arg can giv ris to hazard an pro lems in a wid
partic larly in c emicals, p armac uticals, p trole m an fo d pro e sin in u trie
Be au e of th larg n mb r of in u trial pro e s s that c uld b in olv d it is n t p s ible
to giv d taie informatio rele ant to al of th m In tead, this d c me t atempts to
th m This informatio s o ld e able th plant o erator to tak whate er pre autio s c uld b
n c s ary to av id ig itio s of p te tialy flammable atmo p ere an ele tro tatic s o k
For c n e ie c this d c me t is divid d into a n mb r of clau e Th s d al with pro lems
Trang 26© IEC 2 17
f ele tro tatic pro lems cau e b p o le;
g) av idan e of ele tro tatic s o k;
h) earthin an b n in of plant an mac in ry;
As this d c me t is v ry c mple , c re tly e aluatin th ele tro tatic hazard of pro u ts
an pro e s s may n t b eas for n w read rs For this reas n a u iv rsal y ap l cable
informativ An e F has b e ap e d d whic refere c s th rele ant s ctio s of this
d c me t in th c r e t ord r
It is v ry s ld m that an ele tro tatic hazard can b treate b its lf Pre autio s again t
ele tro tatic hazard s o ld b in ad itio to oth r pre autio s, e.g e plo io prote tio
Th y s o ld als b c n iste t with pre autio s tak n to av id oth r hazard that may b
pre e t, s c as ig itio s d e to oth r cau e , an to icity It is imp rtant that al s urc s of
ris in a s stem of work are c n id re an that a balan e ap roac to safety that c v rs al
ris s is ad pte In partic lar, care s o ld b e ercis d in th pro isio of earthin s stems
wh re th y can interfere with oth r prote tiv s stems, e.g cath dic prote tio or intrin icaly
safe ele trical e uipme t
6 Static electricity in sol d materials
6.1 General considerations
Sol d materials are u ual y c aracteris d as in ulatin , dis ipativ or c n u tiv ac ordin to
th ir v lume re istivity En lo ure are u ual y clas ifie ac ordin to th ir s rfac re istan e
or re istivity (meas re ac ordin to IEC 6 0 9-0, IEC 6 16 , IEC 6 0 3 or IEC 613 0-2-3 or
e uivale t meth d ) Meas rin d tais wi als b d alt with in IEC 6 0 9-3 -2
2
s rfac clas ificatio s are e uivale t b cau e th s rfac re istivity is te time hig er than
th s rfac re istan e for th s e ifie ele tro e g ometrie For oth r s e ific ap lcatio s
difere t d finitio s may b ap l cable (e.g leakag re istan e in th cas of flo rs) Th
thre h ld mo t c mmo ly u e for th s p rp s s are s own in Table 1
—————————
Trang 27© IEC 2 17
Table 1 – Bo ndary l mits at (2 ± 2) °C an (2 ± 5) % RH for the chara teris tion
of sol d materials an example for the cla sific tio of obje ts
as embly (Ω)
a
Wh re local ambie t co ditio s are sig ifica tly difere t from th state worst case test co ditio of
(2 ± 2)°C a d (2 ± 5) % RH, oth r test co ditio s may b use afer a careful h zard e alu tio In some
co ntries, esp cialy d rin winter, a relativ h midity of (12 ± 3) % at (2 ± 2) °C is a a pro riate test
e viro me t for q alfyin e uipme t As th resista ce of n n-metals usu ly d p n s stro gly o th
me surin v lta e, th me surin v lta es (ypicaly 5 0 to 1 0 0 V) sh uldb ch se to b co siste t with
th p rp se of th me sureme t a d state with th test result
b
Ac ordin to ISO 8 31, th v lu s for h ses are me sure at (5 ± 5) % RH a d are th latest o es ta e
from Ta le 15 in 7.7.3.1 In th p st, slg tly difere t v lu s h v b e use in ISO a d CE ELEC
d cume ts Oth r clas ificatio s may b use by in ustry sta d rds for sp cific a plcatio s (e.g in
ISO 8 31 co d ctiv h ses for in ustry a plcatio s, dis ip tiv a tistatic h ses for a tomo ie a plcatio s)
which d esn t n ces ariy imply electrostaticsafety
En lo ure criteria are to pre e t trib -c argin an th s d n t n c s ari y dis ipate c arg
d p site from u s e ifie pro e s s within th e clo ure
Difere t valu s meas re at 5 % RH hav b e ap le in th past in th ab e c of a
d h midifie te t c amb r an are c n id re to er o th safe sid This ap roac has n w
b e dis o tin e , an lmits at 5 % RH are, e c pt for h s s, giv n in oth r d c me ts
o ly Th y s o ld o ly b u e if an ap ro riate clmate is n t avaiable As th c arg abi ty
of materials is hig er at 2 % RH c mpare to 3 % RH, th former valu of 3 % RH has
b e re u e to (2 ± 5) % RH A relativ h midity at th lower part of th interval s o ld b
ap l e d rin meas reme ts wh n v r p s ible
Wh n c aracterizin n n-h mo e o s materials th meas re valu s s o ld b av rag d
an ro n e to th n are t ord r of mag itu e u le s oth rwis s e ifie b th te t meth d
No -h mo e e u materials may e hibit difere t re istivity in difere t dire tio s
In tead of meas rin re istan e, th rate of c arg d cay may b u e to c aracteriz th
dis ipativ b havio r of clothin (s e EN 1 4 -3 an EN 1 4 -5)
Ele trical y in ulatin s l d materials are c mmo ly u e in man forms, in lu in pip s,
c ntain rs, s e ts, c atin s an ln rs Th u e of ele tricaly in ulatin s l d materials in
hazard u areas can giv ris to man ele tro tatic hazard , in partic lar:
Trang 28© IEC 2 17
a) c n u tiv o je ts c uld b is late from earth b th material an c uld th n reac a
hig ele trical p te tial an giv ris to s ark (s e A.3.2);
b) c arg s o th s rfac of th material c uld lead to bru h dis harg s (s e A.3.4);
c) a c mbinatio of c n u tiv an in ulatin materials in th pre e c of prolfic c arg
g n rators (s e 12.3) c uld lead to e erg tic pro agatin bru h dis harg s (s e A.3.5)
Meas re to ad re s th s hazard are giv n in 6.2, 6.3 an 6.4
If in ulatin materials are u e , a ris as e sme t is n c s ary to id ntify if th re is an
pro e s that can lead to dire t pro u tio of or in ire t in u tio of ele tro tatic c argin o
in ulate materials that are pre e t in th lo atio
6.2 The us of con uctive or dis ipative materials in pla e of insulating o e
6.2.1 General co sideratio s
It is g n ral y g o practic to minimis th u e of in ulatin materials in hazard u areas
Whie this may b ac ie e primari y b th u e of in ere tly c n u tiv materials (e.g
metals), man materials whic u e to b avai able o ly in in ulatin forms (e.g ru b rs or
plastic ) are n w avai able in grad s whic me t th re uireme ts to b c n id re
c n u tiv or dis ipativ as giv n in T ble 1 This in reas in c n u tivity is ty icaly
ac ie e eith r b ad in c n u tiv in re ie ts (e.g carb n blac ) to its c mp sitio , or b
ap lyin h gro c pic ag nts to its s rfac that atract atmo p eric moisture − c n u tiv
p lymers, laminate with c n u tiv eleme ts an metal s d fims hav al b e d v lo e
for impro e static dis ipatio
It is imp rtant that s c c n u tiv an dis ipativ materials are earth d relably ac ordin to
Clau e 13 an are lo g lastin ac ordin to Clau e 13 Als , if c n u tiv or dis ipativ
c atin s are u e to mak an in ulatin material n n-c arg able, it is imp rtant that s c
c atin s are pro erly earth d, an that th ir d rabi ty an s itabi ty for u e in hazard u
areas (partic larly Zo e 0 an Zo e 1) is d mo strate for th partic lar ap lcatio
An th r c n id ratio is that th u e of a hig pro ortio of ad itiv s s c as carb n blac
may d grad th p y ical pro ertie (primariy stre gth an c emical re istan e) of th
material This may re d r s c materials u s itable for c rtain ap lcatio s This can b
av id d b u in intrin ical y c n u tiv p lymers as a c n u tin in re ie t or c atin Care
s o ld b tak n to e s re s f icie tly hig c n e tratio s of dis ipativ ad itiv s an th ir
u iform distrib tio
NOT It is n t p s ible to d termin wh th r materials may b dis ip tiv or co d ctiv by th ir colo r Black
p lymers may n t b dis ip tiv , a d mo ern co d ctiv or dis ip tiv materials may b a aia le in a v riety of
colo rs
F bric , e.g fiter cloth, can b mad dis ipativ b in orp ratin stainle s ste l or oth r
c n u tiv or dis ipativ fibre in th fabric Care has to b tak n to e s re that, as a re ult
of was in or me hanical stre s, th o eral c n u tivity of th fabric is maintain d an
is late patc e of c n u tiv fibre are n t forme
6.2.2 Dis ipative sol d materials
A s ld material is d fin d as dis ipativ if its s rfac re istan e, s rfac re istivity or v lume
re istivity me t th c mbin d criteria s t o t in 6.1
In g n ral, pro idin that dis ipativ materials are c n e te to earth ac ordin to Clau e 13,
n furth r prote tiv meas re n e to b tak n Howe er, in pro e s s in olvin hig s e d
s paratio (e.g c n e or an tran mis io b lts, s e 6.4) lower re istivitie an re istan e
can b re uire
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NOT 1 For materials with resistivities at th to e d of th dis ip tiv ra g th re wi b sig ifica t co straints
o th p s ible g ometry of a ma ufacture item if th re uireme ts of Cla se 13 are to b met (e.g lo g pip s or
thin fiame ts wi n t me t th e rthin re uireme ts whist thin sh ets with a larg e rth co tact are wi )
In s me cas s, partic larly with plastic fims or s e tin , a material is ad e to at ract
atmo p eric moisture to th s rfac , th s in reasin s rfac c n u tivity Care s o ld b
tak n wh re this ty e of dis ipativ plastic fim or s e tin is u e in low h midity c n itio s:
in e viro me ts with low h midity ( y ical y < 0 %), it can b c me in ulatin an ac umulate
ele tro tatic c arg
It s o ld b e s re that a dis ipativ c atin can ot b was e away or ru b d of an
can ot lo e its efe tiv n s o er time Oth rwis s c a c atin wo ld o ly b ap ro riate
as a temp rary meas re to re u e ac umulatio of static ele tric c arg
Dis ipativ ag nts u e in pac agin s o ld b c mpatible with th pro u t c ntain d within
th pac ag Ab orptio of th dis ipativ ag nts b pro u t with whic it is in c ntact may
cau e pro u t c ntaminatio an / or lo s of dis ipativ pro ertie of th pac ag
NOT 2 New static dis ip tiv a ditiv s are a aia le which incre se th v lume resistivity a d are, th refore,
les se sitiv to h midity b t are also afecte by a in as are oth r a ditiv s
NOT 3 Th resista ce of dis ip tiv materialsma e from ru b r v lca ize with carb n black may incre se with
d cre sin temp rature Such materials may, for example, b dis ip tiv (~10 MΩ) at 2 ˚C b t insulatin
(~10 TΩ) at 0 ˚C
6.2.3 Earthing of con uctive an dis ipative items
Al metal an oth r c n u tiv or dis ipativ material s o ld b c n e te to earth ac ordin
to Clau e 13 with th e c ptio of v ry smal items Th capacitan e of is late items
d p n s o th ir siz , s ro n in materials an pro imity to oth r c n u tors an may b
v ry difere t u d r in tale or n n-in tale c n itio s Th maximum al owable capacitan e
of is late items d p n s o th ig itabi ty of th gas s, vap urs an d st e pre s d b th
re re e tativ gas gro p I I A, I B an I C (IEC 6 0 9-2 -1, s e D.3) or d st gro p I
IEC 6 0 9-10-2, s e D.2) as s own in T ble 2, takin ac o nt of th fol owin :
a) Capacitan e b low 3 pF n e n t b earth d pro id d that th o je t can ot reac a
hazard u p te tial an is n t situate in Zo e 0 wh n gas s or vap urs b lo gin to
Gro p I C are u e
b) In Zo e 1 wh re gas s or vap urs b lo gin to Gro p I A are u e , an in Zo e 2 an
21 th maximum alowe is late capacitan e may b in reas d to 6 pF pro id d hig
c argin pro e s s d n t o c r
c) In d st Zo e 2 an 21 an in Gro p I th maximum al owe is late capacitan e may
b furth r in reas d to 10 pF pro id d that eith r hig c argin pro e s s d n t o c r or
o ly p wd rs with minimum ig itio e ergie hig er than 10 mJ are han le
d) Th l mits in T ble 2 are n t ab olute valu s that pre e t in e div dis harg s, b t th y
merely re u e th ris of o c r e c to a g n raly ac e te low le el
e) Han h ld d vic s an han to ls are e p cte to b earth d via th u er In an cas of
d u t th u er s o ld e s re earthin of th d vic wh n workin in hazard u areas
f Pe ple are c n u tiv items havin s ficie t capacitan e to pro u e an in e div
dis harg Th y, th refore, s o ld b earth d ac ordin to Clau e 1 b fore e terin a
hazard u area Zo e 0, 1, 2 , 21 or Gro p I
Capacitan e s o ld b meas re ac ordin to IEC 6 0 9-0, 2 15
NOT It is s h d le to re ise thismeth d a d mo e it to IEC 6 0 9-3 -2
—————————
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Table 2 – Maximum al owed isolated c pa itanc in Zo e with ex losive atmosp ere
ca a le of g n ratin h zard us p te tials
NOT 1 Th su divisio s are b se o th maximum exp rime tal safe g p (ME G) or th minimum ig itio
cure t ratio (MIC ratio) of th explosiv g s atmosp ere in which th e uipme t may b instale (se
IEC 6 0 9-2 -1) More d tais ca b fo n in C.6 a d D.3
NOT 2 Ma u l ru bin isusu ly n t co sid re to b a hig ch rgin proces
For dis ipativ materials with a s rfac re istan e e c e in 10 GΩ earthin may n t b
n c s ary In an cas of d u t an ad itio al te t is n c s ary to pro e ele tro tatic safety of
u earth d o je ts (e.g 6.3.9)
6.3 Pre autio s required when usin insulatin sol d materials
6.3.1 General
Th re trictio s o th u e of in ulatin materials in hazard u areas d p n o th
clas ificatio of th hazard u area ac ordin to IEC 6 0 9-10-1 an IEC 6 0 9-10-2:
a) in Zo e 0, in ulatin s l d materials s o ld o ly b u e if c argin pro e s s capable of
g n ratin hazard u p te tials wi n t o c r eith r d rin n rmal o eratio in lu in
mainte an e an cleanin or e e in th cas of rare malfu ctio s;
b) in Zo e 1, in ulatin s l d materials s o ld o ly b u e if c argin pro e s s capable of
g n ratin hazard u p te tials wi n t o c r eith r d rin n rmal o eratio in lu in
mainte an e an cleanin or in th cas of l k ly malfu ctio s;
c) in Zo e 2, in ulatin s l d materials s o ld o ly b u e if c argin pro e s s capable of
g n ratin hazard u p te tials are u l k ly to o c r d rin n rmal o eratio in lu in
mainte an e an cleanin
pro agatin bru h dis harg s (s e A.3) Howe er, practical e p rie c , e p rime tal
e id n e an th ab e c of in id nts in icate that bru h dis harg s d n t ig ite e e
ig itio s n itiv p wd r clo d in th ab e c of an flammable gas or vap ur
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NOT 1 Synth tic fa ric use in cloths for cle nin or wipin ca d v lo suficie t static electric ch rg to
pro uce dis h rg s ca a le of ig itin solv nt v p urs Typicaly, ch rg g n ratio incre ses with th sp e a d
vig ur of th wipin actio Th material b in cle n d or wip d, if insulatin , also ca ac umulate suficie t
ch rg to pro uce a ince div dis h rg Coto or s nth tic fa ric tre te with a static dis ip tiv comp u d
may b re uire if static electric ch rg g n ratio n e s to b co trole , esp cialy if flamma le insulatin
solv nts are b in use for cle nin or wipin
NOT 2 Th prese ce of co tamin tio (e.g gre se or moisture) may afect th p te tial ig itio h zard wh n
usin insulatin materials
NOT 3 Co d ctiv solds, o jects or lq ids may form h zard us isolate co d ctiv isla ds if prese t o
ch rg d insulatin surfaces
In ad itio , to pre e t in e div dis harg s th pre autio s giv n in 6.3.2 to 6.3.4 s o ld b
tak n in al Zo e wh re th u e of in ulatin s l d materials is u av idable Th pre autio s
giv n in 6.3.2 to 6.3.4 relate to th av idan e of in e div bru h dis harg s, that giv n in
6.3.4 als relate to pro agatin bru h dis harg s
6.3.2 Re trictio s on the siz of charge ble insulating surfa e
Wh re th u e of c arg able in ulatin material in a hazard u area is n c s ary, th
maximum al owable siz of in ulatin s rfac d p n s o th ig itabi ty of th gas s an
vap urs e pre s d b th re re e tativ gro p I I A, I B, I C (IEC 6 0 9-2 -1) or th
re re e tativ d st gro p I (IEC 6 0 9-0) an th clas ificatio of th hazard u area
(IEC 6 0 9-10-1 an IEC 6 0 9-10-2, s e D.2) as s own in T ble 3, takin ac o nt of th
folowin :
a) for s e t materials th area is d fin d b th e p s d (c arg able) area;
b) for c rv d or ir e ularly s ap d o je ts th area is th proje tio of th o je t givin th
maximum area;
c) for lo g narow materials, s c as cable s eath or pip s, th maximum siz is d fin d b
th tran v rs dime sio (i.e th diameter for a cable s eath or pip ); alth u h wh n it is
c ie it s o ld b treate as for a s e t;
d) e e smaler diameters can b re uire for narow pip s or tu e c ntainin flowin
l q id or p wd rs;
e) n rmal ele tric cable are u ual y ac e table in al z n s Se IEC 6 0 9-14 Very thic
in ulatin lay rs o thic cable s o ld, h we er, b te te e p rime tal y e.g ac ordin
to IEC 6 0 9-0:2 0 , 2 14
NOT It is s h d le to re ise thismeth d a d mo e it to IEC 6 0 9-3 -2
It is e s ntial that n n-c n u tiv s l d materials u e in hazard u areas d n t e c e th
maximum area or width valu s giv n in T ble 3 for th z n within whic it is u e u le s it
can b e p rime tal y s own that hazard u ele tro tatic c arg s are n t to b e p cte
(s e 6.3.9) or c argin me hanisms wi n t o c r at an time An e ample of th last name
cas is sig s or lamp at th c i n whic are n rmal y n t e p s d to an c argin
me hanisms In this cas , a warnin “Clean with a water-wet cloth o ly an al ow to dry
naturaly” is s ficie t to av id c argin wh n cleanin
—————————
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Table 3 – Re trictio on siz of insulatin sol d materials in ha ard us are s
Max
are
(mm2
) Max
width
(mm) Max
are
(mm2
)Max
) Max
)Max
)Max
NOT 2 Eq ipme t mark d I B is suita le for a plcatio s re uirin Gro p I A e uipme t Simiarly, e uipme t
mark d IC is suita le for a plcatio s re uirin Gro p I A or Gro p I B e uipme t
NOT 3 Th se b rd r lmits are also use e.g in IEC 6 0 9-0, CE ELEC TR 5 4 4, TRB 215 , JNIOS
TR4 , a d B 5 5
NOT 4 Th su divisio s are b se o th maximum exp rime tal safe g p (ME G) or th minimum ig itio
cure t ratio (MIC ratio) of th explosiv g s atmosp ere in which th e uipme t may b instale (se
IEC 6 0 9-2 -1) More d tais ca b fo n in C.6 a d D.3
NOT 5 Th lmits in Ta le 3 are n t a solute v lu s th t pre e t ince div dis h rg s, th y merely re uce it
to a g n raly ac e te low le el
NOT 6 Th prese t state of k owle g in icates th t th re is n ig itio risk d e to brush dis h rg s in th
case of se sitiv d sts pro idin th t th re are n flamma le g ses or v p urs (se An ex A.3.4) Howe er,
ch rg g n ratio proces es stro g r th n ma u l ru bin may cre te ince div pro a atin brush dis h rg s
u d r certain circumsta ces (se 6.3.4.2)
6.3.3 Earthed metal me he
Th areas giv n in T ble 3 can b in reas d b a factor of fo r b in orp ratin an earth d
me h (or metal frame) into th in ulatin s l d or b wrap in s c a me h aro n its s rfac
In ad itio :
a) th lay r thic n s ab v th me h s o ld b re tricte to th valu s giv n in 6.3.4.2 to
pre e t bru h dis harg s; an
b) pro agatin bru h dis harg s s o ld b pre e te ac ordin to 6.3.4.3; an
c) s e ial care s o ld b tak n to pre e t or d te t break whic c uld lead to is late
c n u tiv parts whic pre e t a greater ele tro tatic hazard than an in ulatin s rfac
6.3.4 Insulatin coatings o e rthed co ductive surfa e
6.3.4.1 General
L y rs or c atin s of in ulatin s l d o earth d c n u tiv s rfac s (in partic lar metal
s rfac s) can giv ris to bru h an / or pro agatin bru h dis harg s d p n in o s v ral
factors
6.3.4.2 Av idanc of brush dis harge
With re ard to bru h dis harg s, practical e p rie c s ows that th s dis harg s are
u lk ly to b in e div if:
a) hig ele tro tatic c argin pro e s s are av id d (e.g re eate fi in an emptyin of a
c n u tiv drum c ntainin an in ulatin ln r); an ,
Trang 33© IEC 2 17
b) th thic n s of th lay r d e n t e c e a valu of 2 mm in th cas of gas s an
vap urs of gro p I I A an I B an a valu of 0,2 mm in th cas of gas s an vap urs
of gro p I C For d sts th re is n thic n s lmitatio u le s th p wd r lay r can form a
hig re istan e c ntin o s fim, e.g b s lf p lymerizatio or reactio with water
NOT 1 Ma u l ru bin is usu lyn t co sid re to b a hig ch rgin proces
NOT 2 Th thin er th co tin th les ince div are th brush dis h rg s cre te by ma u l ru bin of th
surface, a d th more ince div are th pro a atin brush dis h rg s cre te by stro g r electrostatic ch rgin
proces es o th surface
Howe er, in th cas of flu rinate p lymers an e p rime tal e aluatio of th c arg abi ty
is re omme d d, e.g ac ordin to IEC 6 0 9-0:2 0 , 2 14
NOT It is s h d le to re ise this meth d a d mo e it to IEC 6 0 9-3 -2
6.3.4.3 Av idanc of pro agatin brush dis harge
Pro agatin bru h dis harg s can o c r wh n hig or re eate ele tro tatic c argin
pro e s s act o in ulatin lay rs or c atin s o c n u tiv s rfac s Th s dis harg s can
b pre e te b o e or more of th folowin meas re :
a) Av id havin thin in ulatin c atin s o metals or oth r c n u tiv materials Pro agatin
bru h dis harg s te d to o c r with thin c atin s; th y can n rmal y b pre e te b
havin thic n s e greater than 10 mm;
b) Re u e th s rfac or v lume re istivity of th c atin It is n t k own pre is ly what
le els are re uire to pre e t th o c r e c of pro agatin bru h dis harg s, b t th
valu s for dis ipativ materials giv n in T ble 1 an a leakag re istan e le s than
10 GΩ are k own to b s ficie tly low;
c) Us a c atin with a low diele tric stre gth (break own v ltag for s ld h mo e o s
materials le s than 4 kV, in th cas of wo e fabric 6 kV, s e A.3.5) Su h c atin s
ele tricaly break d wn b fore a pro agatin bru h dis harg can d v lo Th diele tric
stre gth s o ld b meas re ac ordin to IEC 6 2 3-2 in c mbinatio with IEC 6 2 3-1,
or IEC 6 0 9-3 -2
5
d) Av id hig or re eate c argin pro e s s (e.g air io s in th vicinity of hig v ltag
ele tro e , hig s e d flowin l q id an p e matic tran fer of p wd rs, an pap r or
plastic fois tran p rte b mac in s)
NOT 1 Du to th ir slg t p rosity, layers of solv nt or water b se p int or lo se p wd r usu ly h v a low
bre k own v lta e so th t pro a atin brush dis h rg s are dificult to o tain from such layers
NOT 2 Co tin s forme by b kin o a a ple p wd r a d e amel usu ly h v to hig a bre k own v lta e
to a oid pro a atin brush dis h rg s
NOT 3 Polymer fims which are wo n o to a re l or are lfe from a co d ctiv or insulatin surface ca
acq ire bip lar ch rg s ie e u l a d o p site ch rg s o th two surface of th fim This ca le d to brush
dis h rg sa d oc asio aly e e to pro a atin brush dis h rg s
NOT 4 Ma u l ru bin is n t n rmaly co sid re a hig ch rgin proces
6.3.5 Con uctive or dis ipative coatings o insulatin materials
Sp cial care is n c s ary wh n ap lyin a c n u tiv or dis ipativ c atin o an in ulatin
s rfac to e s re a u iform distrib tio of th c n u tiv particle No -u iform distrib tio
may lead to is late c n u tiv islan s whic can b c arg d easi y b in ulate s rfac s in
th ir vicinity Su h is late c n u tiv islan s pre e t a greater ele tro tatic hazard than an
in ulatin s rfac
Co d ctiv c atin s s o ld b earth d as oth r c n u tors in ac ordan e with Clau e 13
—————————
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6.3.6 Static dis ipative agents
Dis ipativ antistatic ag nts are fre u ntly u e o clothin an flo rs an to in reas th
c n u tivity of l q id an materials Care s o ld b tak n to g arante th pre e c of a
s ficie t c n e tratio of th s ag nts to ac ie e th d sire fu ctio For e ample,
dis ipativ ag nts may b c me di ute or was e o t Th refore, th ir efe tiv n s n e s to
b mo itore an maintain d No -migratory p rman nt antistatic p lymer ad itiv s hav
re e tly b e d v lo e to o erc me th s lmitatio s
6.3.7 Humidific tio
Th s rfac re istivity of s me in ulatin s l d materials can b re u e to dis ipativ le els
if th relativ h midity is maintain d ab v ab ut 6 % Ev n th u h damp air is n t
c n u tiv , water / moisture may ad orb o th s rfac of man materials d p n in o th
h dro c pic nature of th material This may b s ficie t to pre e t ac umulatio of static
ele tricity, pro id d th re is a s itable path to earth
Howe er, wh reas th s rfac of s me materials (e.g glas or natural fibre ) can ad orb
e o g moisture to e s re a s rfac c n u tivity that is s ficie t to pre e t ac umulatio of
static ele tricity, oth r materials d n t (e.g p lytetraflu ro th le e or p ly th le e) an are
capable of ac umulatin a static ele tric c arg e e at hig relativ h midity Als , wh n th
h midity fals b low ab ut 3 %, materials whic are s s e tible to h midificatio g n raly
return to b in hig ly in ulatin In reasin th relativ h midity, th refore, is n t ef e tiv in
al cas s an , in g n ral, it s o ld n t b u e as th s le prote tiv meas re This is
partic lar imp rtant in Zo e 0
6.3.8 Io is tio / Charge Neutral s tio
6.3.8.1 General
Io isatio of th air is a meth d of makin th air lo al y io -ric s that c arg s o in ulatin
s ld materials can b n utral s d It is partic larly u eful for n utralsin c arg o in ulatin
plastic s e ts or fi ms Meth d that may b emplo e in lu e th s giv n in 6.3.8.2 to
6.3.8.5 Ne tral satio can ot s c e d if th rate at whic c arg is g n rate e c e s th
rate at whic io s are s p l e to th air, or can migrate to th c arg d s rfac , or if s ficie t
io s of th d sire p larity are n t pre e t Co s q e tly, c re t in talatio an re ular
mainte an e is e s ntial for th s d vic s, takin into c n id ratio factors that can
influ n e th ir efe tiv n s s c as e viro me tal c n itio s (e.g d st an temp rature)
an p sitio in of th d vic in relatio to th material pro e s d, mac in parts, an p o le
Th re u tio of c arg at an o e p int in th o eratio d e n t pre e t g n ratio of
c arg in later ste s of th pro e s, s io is rs may b re uire at a n mb r of lo atio s
Po itio in is imp rtant, an efe tiv n s of in ivid al in tal atio s s o ld b c nfirme b
field meas reme t of re id al c arg or v ltag In partic lar, for fi ms an s e ts it is
n c s ary to e s re that io s are dire te at th c r e t sid to av id formin a bip lar lay r
whic c uld giv ris to pro agatin bru h dis harg s
Coro a p ints remain fu ctio al o ly as lo g as th y are clean an s arp Ac umulatio of
c ntaminants (e.g in , c atin s lutio , or pap r d st an c r o io pro u ts s o ld b
c ntrole b an efe tiv mainte an e pro ram
Io is rs s o ld b s le te b th ir c arg g n ratio rate or b th ir c arg d cay time
Th y s o ld n t b u e in Zo e 1, I C u le s th ris s hav b e e aluate b an e p rt
Furth rmore th y s o ld n t b u e in Zo e 0 as th o ly safety meas re
6.3.8.2 Pa sive io is rs
Pointe ele tro e s c as earth d s arp n e le , fin wire or c n u tiv tin el pro u e
c ro a dis harg s wh n plac d in th ele tric field from a hig ly c arg d s rfac Th s
Trang 35© IEC 2 17
efe tiv n s an may, in ad itio pro u e dis harg s if pas iv io is rs are n t pro erly
earth d
6.3.8.3 Active io is rs
Activ io is rs pro u e io s b ap lyin a hig v ltag to a n mb r of c ro a p ints
Commercial s stems c mmo ly u e alternatin v ltag s in th ran e 5 kV to 10 kV Th u e
of a hig v ltag p wer s p ly el minate th l mitatio of pas iv n utralz rs in c ntrol of
c arg s havin field b low th c ro a o s t thre h ld Th c re ts from th c ro a p ints
are lmite eith r b hig re istan e or capacitiv c u l n
Activ io is rs s o ld b s itable for th lo atio in whic th y are u e an s o ld b
d sig e an c n tru te to pre e t b in a p s ible s urc of ig itio Th y re uire careful
d sig to e s re that th s p ly of io s is balan e with th re uireme ts of th pro e s
6.3.8.4 Radioa tive / sof x-ray io is rs
Radioactiv an s f x-ray s urc s io is th s ro n in air an can b u e to dis ipate th
c arg s from a c arg d b d Su h io isatio its lf d e n t pre e t an ig itio hazard b t is,
h we er, l mite in its efe tiv n s (p rforman e d teriorate with th d cay of th
radioactiv material)
6.3.8.5 Io is d air blowers
Io is d air blowers u in eith r hig v ltag s or radioactiv s urc s are u e mainly for
dis ipatin c arg s from awkwardly s ap d o je ts Howe er, th io c n e tratio can
rapidly d creas d wn tream d e to re ombinatio or ad orptio of th io s b th wals As
a re ult, it is dific lt to c n e th io is d air o er larg distan e Th parts c ntainin th
hig v ltag s s o ld b plac d in a n n-hazard u area u le s th y hav b e ap ro riately
c rtifie
NOT Th fu ctio of a io iser ca b teste byth meth d d s rib d in IEC 613 0-4-7
6.3.9 Meth ds to determine the inc n ivity of dis harge
If th re uireme ts in 6.3.2 to 6.3.8 are n t ap l cable, an e p rime tal d terminatio of a
valu for th in e divity of p s ible dis harg s may b h lpful
On meth d is to c arg th sample u d r worst cas c n itio s as hig ly as p s ible (at
least to th maximum le el that c uld o c r in s rvic ) to pro o e dis harg s to an earth d
MIE valu This meth d is d s rib d in IEC 613 0-4-4
Th maximum c arg tran fer e b a dis harg is ofe u e to giv an in icatio of th
in e divity of s ark an bru h dis harg s in tead of u in an e plo iv gas mixture This
meth d is d s rib d in IEC 6 0 9-0:2 0 , 2 14 T ble 4 s ows a s mmary of al ap l cable
thre h ld lmits
NOT It is s h d le to re ise this meth d a d mo e it to IEC 6 0 9-3 -2
Sp cial care s o ld b tak n to e s re that th te t sample is c arg d as hig ly as p s ible,
that in u e c arg s are c mp n ate for an that o ly o e sin le dis rete dis harg is
re ord d
—————————
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a
Valu s o ly v ld for sp rk dis h rg sfrom u e rth d co d ctiv or dis ip tiv p rts
NOT 1 Th lmits for Zo e 1 a d Zo e 21 e sure th t ince div dis h rg s sh uld n t oc ur d rin n rmal
o eratio Th lmits for Zo e 0 a d 2 are furth r re uce to ac o nt for a n rmal situ tio s a d th hig le el
of safety re uire for th se zo es
NOT 2 For th expla atio of E L se IEC 6 0 9-0 or An ex E
NOT 3 Al of th v lu s co tain a certain safety margin Rece t work in icates th t th v lu hith rto use for
I B co tains a lower safety margin th n al oth r v lu s To e u lze al safety margins th v lu s for I B h v
b e re uce from3 nC to 2 nC
6.4 Co vey r belts and transmis io belts
6.4.1 General
Belts u e for tran mis io of p wer or th tran p rtatio of s ld materials can g n rate a
s paratio of th c ntactin s rfac s (primariy a drivin s af an a b lt Th amo nt of
c arg ac uire d p n s o th material of th c n e or b lt as wel as th materials of th
drivin s af an th rolers, an in reas s with th v lo ity an te sio of th b lt an th
width of th area of c ntact
Th c arg ac uire b th b lt can o ly b safely dis ipate to earth via th earth d
c n u tiv rolers if th c n e or b lt is s ficie tly dis ipativ Material that is s i e from
th e d of a c n e or b lt into a h p er or c ute can car y a sig ificant c arg Co d ctiv or
dis ipativ b lts can ot b e p cte to remo e c arg from an in ulatin c n e e pro u t
b) th s rfac re istan e o b th sid s of th b lt are b low 7 MΩ meas re with th
ele tro e c nfig ratio in 3.21, or
c) in cas s wh re th b lt c n ists of lay rs of difere t materials th b lt is c n id re to b
dis ipativ if th re istan e (meas re at 2 °C an 5 % relativ h midity) b twe n th
two o p site o ter s rfac s is b low 1 GΩ
NOT Surface resista ces me sure ac ordin to ISO 2 4 a d E 14 7 are at (2 ± 2) °C a d (5 ± 5) %
relativ h midity a d with a in er circular electro e of 2 mm in diameter, o ter rin electro e with 12 mm in er
a d 15 mm o ter diameter Surface resista ces me sure with th electro e co fig ratio d s rib d in 3.21 are
exactly fo r times lower
T ble 5 s ows a s mmary of al meas re that are re uire for c n e or b lts ac ordin to
Trang 37dis ip tiv ac ordin to th d finitio of 6.4.2
NOT No informatio isa aia le for b lt v locities > 0 m/s
For e plo io Gro p I th re uireme ts of Zo e 1 (I A & I B) ap ly Howe er, in ulatin c al
d st c n e ors tran p rtin hardly ig itable c n u tiv c al d st an simiar c n e ors may
b u e if a ris as e sme t pro id s a low ris of ig itio
T ble 5 an th re uireme ts in 6.4.2 d n t ap ly to b lts whic dis ipate c arg b c ro a
Su h b lts hav to b te te b e p rts e.g b meas rin th ir c arg abi ty u d r worst
cas c n itio s
A lay r of wax or dirt o th b lt c uld in reas th c arg abi ty of th b lt an als its
re istan e an this c uld in reas th c argin hazard Care s o ld b tak n to e s re that
re airs d n t in reas th valu s giv n It is e s ntial that lay rs of in ulatin ad e iv s
u e to c n e t th b lt d n t inter u t th c n u tiv path
Lig t c n e or b lts as d s rib d in ISO 21 8 -1 fre u ntly hav to c mply with hig ly
s e ial s d c stomer’s d man s For th s cas s, th s e ific stan ard ISO 21 7 , Light
co nve yo r be lts – D ete rmin tio ofe le c tric l re sista ce s an ISO 21 7 , Light c onve yo r b elts
– D ete rmin tio ofth ele ctrostatic field g ene rated b y a ru nning lg ht c nve o r b elt e ist an
6.4.3 Transmis io belts
Tran mis io b lts are V-b lts an flat b lts whic driv rotatin parts or mac in s Th
amo nt of c arg ac uire b th b lt d e to th c ntin o s s paratio of th c ntactin
s rfac s d p n s o th material of th b lt an p le s an in reas s with th v lo ity an
te sio of th b lt an th width of th c ntact area Ac ordin to ISO 9 6 an ISO 1813 a
tran mis io b lt material is d eme to b dis ipativ if:
R × B /L ≤ 6 0 kΩ
wh re L is th distan e b twe n two c n u tiv ele tro e (e.g grap ite, si v r paint, metal
ele tro e) o a tran mis io b lt, B is th width of th flat b lt or d u le th width of th sid
fac of th V-b lt, an R th meas re re istan e b twe n th ele tro e at (2 ± 2) °C, with
n moisture c n e satio
NOT In old r d cume ts (e.g CE ELEC TR 5 4 4), th ac e ta ce criteria was R × B ≤ 10 kΩ m, wh re R is
th resista ce me sure at th in er sid of th mo nte tra smis io b lt b twe n a electro e h lfway b twe n
Trang 38© IEC 2 17
fulfime t of this R × B criterio d p n s o th dista ce b twe n th two p ley it is imp s ible to ch racterise a
b lt material as dis ip tiv For this re so ISO 9 6 a d ISO 1813 giv a dis ip tiv criteria which is in e e d nt
from th le gth of th b lt If th dista ce b twe n two p ley ex e ds 0,6 m th re uireme ts of b th
ISO sta d rds are a tomaticaly fulfi e by th R × B criterio in old r d cume ts state a o e
T ble 6 s ows a s mmary of al meas re that are re uire ac ordin to th clas ificatio of
th hazard u area ac ordin to IEC 6 0 9-10-1 an IEC 6 0 9-10-2:
Table 6 – Req irements for transmis io belts
dis ip tiv ac ordin to th d finitio in 6.4.3
NOT No informatio is a aia le for b lt v locities > 0 m/s
For e plo io Gro p I th re uireme ts of Zo e 1 (I A & I B) ap ly
T ble 6 an th re uireme ts in 6.4.3 d n t ap ly to b lts whic dis ipate c arg b c ro a
Su h b lts hav to b te te b e p rts e.g b meas rin th ir c arg abi ty u d r worst
cas c n itio s
In cas s wh re th b lt c n ists of lay rs of difere t materials th b lt is c n id re to b
dis ipativ if th re istan e acro s it d e n t e c e 1 GΩ (re istan e meas re at 2 °C
an 5 % relativ h midity)
A lay r of wax or dirt o th b lt c uld in reas th c arg abi ty of th b lt an als its
re istan e an this c uld in reas th c argin hazard Care s o ld b tak n to e s re that
re airs d n t in reas th valu s giv n It is e s ntial that lay rs of in ulatin ad e iv s
u e to c n e t th b lt d n t inter u t th c n u tiv path
7 Static electricity in l quids
7.1 General considerations
lq id s rfac temp rature re uire to pro u e a flammable atmo p ere b this pro e s
Howe er, b cau e of th u c rtaintie in olv d in flas p int meas reme t, difere c s
Trang 39© IEC 2 17
e tabl s in l q id s rfac (rath r than b lk) temp rature, it is pru e t to as ume that a
flammable atmo p ere c uld e ist e e wh n th lq id temp rature is b low th flas p int
b a c rtain safety margin Th margin d p n s o th le el of u c rtainty ab ut temp rature,
lq id c mp sitio etc For wel-c ntrol e c n itio s a margin of 5 °C for p re lq id an at
least 1 °C for mixture is ty ical y n e e
Wh re tan s are e p s d to dire t s nl g t an lq id temp rature are n t mo itore it
s o ld b as ume that a flammable atmo p ere c uld b pre e t wh n han ln lq id with
flas p ints u to 6 °C In areas of hig ambie t temp rature an stro g s nl g t, flammable
atmo p ere may o c r e e with lq id that hav flas p ints ab v 6 °C
Wh n han l n a l q id at a temp rature that is wel ab v its flas p int, th saturate
vap ur may giv an o er-ric (i.e n n- lammable) atmo p ere Howe er, th actual
atmo p ere ab v th lq id may n t b saturate (e.g b cau e of v ntiatio ) an s may b
flammable It is th refore n c s ary to as ume that th atmo p ere c uld b flammable
u le s it can b s own oth rwis Co s q e tly, for low flas -p int lq id , th pre e c of
an o er-ric atmo p ere s o ld n t g n ral y b rel e u o as th o ly c ntrol meas re
In s me circ mstan e , th flammable atmo p ere is n t d e to th l q id b in han le b t
d e to re id e of v latie lq id or vap ur from earler o eratio s with th same e uipme t or
from n arb o eratio s Re id al vap urs can o c r d rin switc loadin , in whic a lq id
havin a hig flas p int (e.g die el) is load d into a tan whic pre io sly c ntain d a l q id
with a low flas p int (e.g gas ln ) A hig pro ortio of road tan er fire has b e
as o iate with switc -loadin
7.1.2 Ig itio s nsitivity and lmitatio s to the s o e of ad ic
Th s n itivity of a flammable atmo p ere to ele tro tatic ig itio d p n s o th
c n e tratio an minimum ig itio e erg (MIE − s e C.6) of th flammable material A
h lpful rule of th mb is that th mo t easiy ig itable vap ur c n e tratio is ap ro imately
d u le th c n e tratio at th lower flammable lmit Be au e of th c n e tratio ef e t, a
mixture mad with a hig MIE material at its mo t easi y ig itable c n e tratio may b more
s n itiv to ig itio than a mixture mad with a low MIE material at a vap ur c n e tratio
that l e o ly ju t within th flammable ran e
For e ui brium vap ur/air mixture create b flammable l q id , th mo t easi y ig itable
vap ur c n e tratio is ty ical y ac ie e at temp rature of ap ro imately 10 °C to 2 °C
ab v th flas p int Flammable l q id of interme iate v lati ty te d to pro u e th ir mo t
easi y ig itable mixture at c mmo ambie t temp rature : s c lq id in lu e tolu n
( las p int 6 °C), pro yl ac tate ( las p int 10 °C) an ac to itrie ( las p int 2 °C)
Th g n ral pre autio s giv n in this c apter are d sig e to pre e t th ig itio of materials
with MIEs of 0,2 mJ or more wh n pre e t at th mo t easi y ig itable vap ur c n e tratio
Th y are th s ap l cable to th mo t easiy ig itable mixture in air of th vap urs of c mmo
flammable l q id s c as parafinic an aromatic s lv nts, h dro arb n fu ls an man
organic s lv nts (s e l st of MIE in T ble C.2) At ty ical ambie t temp rature , th safety
margin are at a minimum wh n han ln flammable lq id of interme iate v lati ty s c as
th s lste ab v In s c o eratio s, partic lar care s o ld th refore b tak n to e s re
that al re omme d d pre autio s are di g ntly fol owe
Alth u h Ex lo io Gro p are n t as ig e o th basis of MIE (s e C.6), th pre autio s
re uire in th pre e c of mo t Ex lo io Gro p I A vap urs are lk ly to b simi ar to th s
giv n h re for MIEs of 0,2 mJ an ab v Ad itio al pre autio s are, h we er, lk ly to b
re uire wh re th atmo p ere ab v th l q id is more s n itiv to ig itio This situatio
wi aris , for e ample, with th mo t readiy ig itable mixture in air of v latie materials that
hav MIEs of le s than 0,2 mJ (mo t Ex lo io Gro p I B an I C materials) or with o y e
-ric mixture Alth u h g n ral ad ic has n t b e d v lo e for th s more s n itiv
atmo p ere , re omme datio s are giv n for a few s e ific activitie Wh re th y are giv n,
th ad itio al pre autio s for th more s n itiv materials are e plcitly id ntifie as s c in
Trang 40© IEC 2 17
7.1.3 Chargin me hanisms
Liq id can b c me ele tro tatical y c arg d wh n th y mo e relativ to c ntactin s ld or
if th re are two or more immis ible l q id p as s an th re is mo eme t Th s rayin of
lq id can als create a hig ly c arg d mist or s ray Furth r d tai s of c arg g n ratio
an c arg ac umulatio in l q id are giv n in A.1.3 to A.1.7 (g n ratio ) an A.2.2
(ac umulatio )
7.1.4 Charge a cumulatio an con uctivity cla sific tions
Th le el of c arg ac umulatio in a partic lar lq id, an th refore th ele tro tatic hazard
that can b create , is stro gly d p n e t u o its ele trical c n u tivity an diele tric
c n tant (relativ p rmitivity), ε
r To d s rib th p s ible hazard an as o iate mean of
pre e tio , th c n u tivitie of l q id hav b e clas ifie as fol ows:
For l q id with a diele tric c n tant that is s b tantialy hig er than 2 or for lq id wh s
diele tric c n tant is u k own, th b rd r lmit for low c n u tivity is u ual y s t to 10 pS/m
Th u p r b rd r lmit of me ium c n u tivity remain at 10 0 0 pS/m
NOT 10 pS/m is co sid re suficie t for u k own cases b ca se few, if a y, low co d ctivity lq ids h v a
relativ p rmitivity sig ifica tly hig er th n 4
Hazard u le els of c arg ac umulatio are mo t c mmo ly as o iate with lq id of low
c n u tivity Howe er, th y can o c r with me ium or hig c n u tivity lq id in pro e s s
that pro u e mists or s ray , wh n tran p rtin me ium c n u tivity l q id thro g
in ulatin pip s or d rin two-p as mixin o eratio s
In g n ral, p lar s lv nts s c as alc h ls, k to e an water hav a hig c n u tivity, whi e
c n u tivitie an relaxatio time for a n mb r of lq id are giv n in T ble 7
NOT 1 A more complete lst inclu in a wid r ra g of lq ids a d dielectricco sta t d ta isgiv n in N P -7
NOT 2 Biofu ls a d hydrocarb n fu ls ble d d with biocomp n nts ca h v a wid ra g of co d ctivity
d p n in o th ir comp sitio
NOT 3 Test meth ds for me surin th co d ctivity of a lq id are giv n in e.g A TM D4 0 -9 , DIN 51412-1,
DIN 51412-2 a d ISO 6 9