Explosion Protection Directives and Basic Principles...2002/01/11 · EN 2.002.1/11.17 6 3....

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Explosion ProtectionDirectives and Basic Principles

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and Basic Principles

NoteThis brochure contains general information relating to explosion protection. It was compiled with care and it takes into account the legal regulations and standards that applied at the point of going to press. Nevertheless, it is not possible to eliminate all risk of the brochure containing incorrect or misleading statements. The statements it contains cannot be used for an evaluation or a risk assessment of a specificsystem.

Forspecificapplicationsoroperatingconditions,please contact the relevant technical department.

Subjecttomodifications

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Contents

1. Introduction ...........................................................................................................................52. What are explosions and how are they caused? ...............................................................53. Explosion protection .............................................................................................................63.1. Primaryexplosionprotection ...................................................................................................63.2. Secondaryexplosionprotection ..............................................................................................63.3. Tertiaryexplosionprotection(constructionalexplosionprotection) .........................................64. Flammable substances .........................................................................................................74.1. Flammable gases and vapours ...............................................................................................74.2. Flammablefluids .....................................................................................................................74.3. Flammable solids ....................................................................................................................84.4. Explosion limits........................................................................................................................84.5. Maximumexperimentalsafegap(MESG) ..............................................................................94.6. Minimumignitionenergy,minimumignitioncurrent ................................................................94.7. Groups...................................................................................................................................105. Temperature classes ...........................................................................................................115.1. Gases/vapours ......................................................................................................................115.2. Dusts .....................................................................................................................................126. Ignition sources...................................................................................................................136.1. Hot surfaces ..........................................................................................................................136.2. Flames, hot gases and particles............................................................................................136.3. Mechanicallygeneratedsparks .............................................................................................136.4. Electrical apparatus ...............................................................................................................136.5. Strayelectriccurrents,cathodiccorrosionprotection............................................................146.6. Staticelectricity .....................................................................................................................146.7. Lightning ................................................................................................................................146.8. High-frequencyelectromagneticwaves (radiowaves,microwaves;frequency:104 Hz–3*1011Hz) ....................................................146.9. Electromagnetic waves (infraredtoUVradiation;frequency:3*1011 Hz–3*1015Hz) ...................................................146.10. Ionising radiation ...................................................................................................................146.11. Ultrasound .............................................................................................................................156.12. Adiabaticcompression,shockwaves,flowinggases ............................................................156.13. Exothermic reactions .............................................................................................................157. Classificationandcategorisationofequipment forexplosiveatmospheres .................................................................................................157.1. Equipmentgroupsasdefinedby2014/34/EU .......................................................................157.2. Equipment categories............................................................................................................167.3. Typesofexplosiveatmosphere .............................................................................................167.4. Zonedivisionsasdefinedbydirective1999/92/EC...............................................................177.5. Criteriafortheselectionofequipmentandprotectivesystems .............................................198. Equipmentprotectionlevel ................................................................................................199. Typesofignitionprotection ...............................................................................................209.1. Flameproof enclosure, electrical ignition protection ..............................................................229.2. Pressurised enclosure ...........................................................................................................229.3. Powderfilling .........................................................................................................................239.4. Liquid immersion, electrical ignition protection ......................................................................239.5. Increasedsafety ....................................................................................................................249.6. Intrinsicsafety .......................................................................................................................249.7. Ignitionprotectiontype“n_” ...................................................................................................259.8. Encapsulation ........................................................................................................................269.9. Optical radiation ....................................................................................................................269.10. Protectionbyenclosure .........................................................................................................279.11. Flow restricting enclosure......................................................................................................279.12. Flameproof enclosure, non-electrical ignition protection .......................................................289.13. Constructionalsafety .............................................................................................................289.14. Controlofignitionsource.......................................................................................................299.15. Liquid immersion, non-electrical ignition protection...............................................................299.16. Typesofignitionprotection-Mining .....................................................................................30

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10. Marking.................................................................................................................................3010.1. ATEXDirective2014/34/EU ..................................................................................................3010.2. Marking according to standards requirements ......................................................................3110.3. Markings for special conditions .............................................................................................31ATEX marking ................................................................................................................................3211. Explosion protection worldwide and the legal situation .................................................3311.1. Europe – ATEX Directives .....................................................................................................3311.2. Internationalrules–lECEx ....................................................................................................3411.3. USA–NEC............................................................................................................................3411.4. Canada–CEC ......................................................................................................................3411.5. Brazil – INMETRO .................................................................................................................3411.6. EurasianCustomsUnion–TRCU ........................................................................................3411.7. India – PESO.........................................................................................................................3511.8. China–NEPSI ......................................................................................................................3511.9. Korea – KOSHA ....................................................................................................................3511.10. Japan – TIIS ..........................................................................................................................3511.11. Australia, New Zealand .........................................................................................................3512. Comparisonofthemainapprovalregulations ATEX – IECEx – NEC ...........................................................................................................3612.1. ATEX .....................................................................................................................................3612.2. IECEx ....................................................................................................................................3612.3. NEC500–504 ........................................................................................................................3712.4. NEC505–506 ........................................................................................................................3813. Bibliography ........................................................................................................................39

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1. Introduction

In sectors such as the chemical and pharmaceutical industries, in mining, in the production of crudeoilandnaturalgasandinthefoodindustry(particularlyinmills),flammablesubstancesareworked with in various processing and manufacturing procedures. This means that dangerous situationscontinuallyarisethatcanresultinexplosionsandjeopardisepeople’ssafety.

2. What are explosions and how are they caused?

Anexplosionreferstoanabruptchemicalreactionthatoccursbetweenaflammablesubstanceandoxygen,releasinglargeamountsofenergy.Thisreactionresultsinanincreaseintemperatureand/orpressure(expansionspeed:1to1,000m/s).

Description Expansion speedDeflagration 0.1–1 m/s Explosion 1–1,000 m/s Detonation 1,000 m/s or more

Table:Deflagration,explosion,detonation

Adeflagrationistheweakestformofexplosivecombustion.Itresultsinpressuresofmax.1barand expansion speeds of 0.1 to 1 m/s.Threefactorsneedtobepresentsimultaneouslyforanexplosiontooccur:

● Aflammablesubstanceintheformofgases,mists,vapoursordustandlint ● Oxygen(fromtheair) ● A source of ignition

Image:Howanexplosioniscreated

Aspecificratioofflammablesubstancetoairmustbepresentforanexplosiveatmospheretobecreated.Ifthisatmospherecomesintocontactwithasourceofignition(e.g.ahotsurface,electricsparkorelectricarc),themixturewillreactexplosively.Anatmosphereisratedasexplosiveonthebasisoftheatmosphericconditions:anexplosiveatmospherehasapressurebetween0.8and1.1barabsolute(80kPato110kPa)andatemperaturebetween-20and+60°C.Theoxygencontentmustberoughly21%.Thisstandardisationisrequiredasthesafetyparametersareafunctionofpressure,temperatureandoxygencontent.

Explosion ProtectionDirectives and Basic Principles

Ignition source

Oxygen

Flam

mab

le s

ubst

ance

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3. Explosion protection

Varioustechnicaland/ororganisationalmeasurescanbetakentoprovideprotectionfromexplosions.Measuresaretakeninthefollowingorderofpriority:

3.1. Primaryexplosionprotection

Primaryexplosionprotectionmeasuresaimtopreventanexplosiveatmospherefromdeveloping.Avoidingtheuseofflammablesubstanceswouldappeartobethesimplestformofexplosionprotection(i.e.usingalternativetechnologies).However,intheareasofapplicationmentionedabove,thisispracticallyimpossible.Itmightthenbepossibletoavoidorrestrictthereleaseofflammablesubstancestopreventexplosivemixturesfromforming,bothinsideandaroundpipefittings.Oftenamoreopendesigncombinedwithairsupplyandventingisenoughtoprovideappropriate help.Anotheroptionistoreplaceorreducetheamountofoxygenintheairbysystematicallyaddingnitrogen or carbon dioxide. This is referred to as inerting. It is, of course, not possible to replace theoxygeninallareaswherepeoplearepresent.

3.2. Secondaryexplosionprotection

Ifahazardousexplosiveatmospherecannotbeprevented,secondaryexplosionprotectionmeasures are taken. These measures aim to stop a hazardous atmosphere from being ignited. Thefollowingignitionprotectionmeasurescanbeapplied:

● Avoiding ignition sources ● Dividing the explosive areas up into zones ● Usingexplosion-prooftoolsandmaterials ● Usingprotectiondevices

Allignitionprotectionmeasurestakenforequipmentinpotentiallyexplosiveareasarepartofsecondaryexplosionprotection.

3.3. Tertiaryexplosionprotection(constructionalexplosionprotection)

If ignition sources and thus explosion hazards pose a threat despite the above-mentioned measuresbeingtaken(e.g.asaresultofelectrostaticdischargeorchemicalreactions),theeffectsofanexplosionordetonationmustbelimitedtoanacceptableextent.Thisisdonebytakingconstructional,ortertiary,explosionprotectionmeasures.A design that is resistant to explosion pressure is the most common constructional measure – it is not able to prevent an explosion from happening but can restrict the damage it causes. The equipment must be built to withstand the maximum explosion pressure, and in extreme cases even the detonation pressure.In pipes and even in elongated designs, a detonation can develop in little time. If the explosion-proof design is not able to cope with the increased pressure, effective explosion-relief or pressure-relief devices need to be installed. A further measure is to use extinguishing devices to suppress an explosion.

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4. Flammable substances

Flammablesubstancescanbegaseous,fluidorsolid.Theyarenormallyratedaccordingtotheirreactivitywiththeoxygenintheair.

4.1. Flammable gases and vapours

Aflammablegascansometimesbeanelementarygassuchashydrogen,butflammablegasesaremuchmoreoftencompoundsthatcontaincarbonandhydrogen.Theseflammablegasesandvapoursrequireonlysmallamountsofenergytoreactwithatmosphericoxygen.Vapoursarethepartsoffluids–inthecontextoftheexplosionprotectionofflammablefluids–that have entered the ambient air as a result of the vapour pressure above a liquid surface, around a liquid jet or around droplets. Mists constitute a special form, which can be treated as vapours in terms of their explosion behaviour.

4.2. Flammablefluids

Flammablefluidsareabletomixwiththeambientairtoformaflammablevapour/airmixtureundercertainconditions.Commonflammablefluidsarehydrocarboncompoundssuchasether,acetoneorpetroleumspirit.TheCLPRegulationclassifiesthesefluidsasflammable, highlyflammable or extremelyflammable,dependingontheirflashpointandboilingpoint.Animportantcharacteristicforflammablefluidsistheflashpoint.Theflashpointisthelowesttemperatureatwhichaflammablefluid,understandardisedtestconditions,allowsasufficientquantityofvapourtobegeneratedatitssurfacetoenablethevapour-airmixturetobeignitedbyaneffectiveignitionsource.Theflashpointisimportantintheratingofpotentiallyexplosiveareas.Flammablefluidswithhighflashpointtemperaturesarelesscriticalthanthosewithaflashpointatroom temperature or below. Sprayingflammablefluidsfromspraycansorinpaintingfacilitiescancreatemists.Suchcloudsofmistaremadeupofverysmalldropletsandtheyareabletoexplode.Inthiscase,theflashpointisofminorimportance.Thesafetyconsiderationsforflammablegasesapplytogases,vapoursandmistsconsistingofflammablefluids.

Hazard category Descriptionofthe flammablefluid

Flash point and initial boiling point

1 Extremelyflammable liquidandvapour(H224)

Flashpoint<23°C Initialboilingpoint≤35°C

2 Highlyflammable liquidandvapour(H225)

Flashpoint<23°C Initialboilingpoint>35°C

3 Flammable liquidandvapour(H226) 23°C≤flashpoint≤60°C

Table:ClassificationofflammablefluidsinaccordancewiththeCLPRegulation

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4.3. Flammable solids

Flammablesolidsintheformofdustorlintcanreactwithatmosphericoxygenandproducedisastrousexplosions.Dustbehavesdifferentlydependingonwhetherittakestheformofadustdepositoradustcloud.Dustdepositscanigniteonhotsurfacesandcausesmoulderingfires.Dustclouds,ontheotherhand,candirectlyresultinanexplosionwhenenergyisintroducedlocallyoroncontactwithhotsurfaces.Itnormallytakesmoreenergytotriggeranexplosioninmixtureswithairthaningasesandvapours.However,oncethecombustionstarts,theenergyreleasedbythecombustionreactionproducessuchhightemperaturesandpressuresthatthecombustionturnsintoanexplosion.Accordingly,smoulderinglayersofdustcancauseadustexplosioniftheyaredisturbedtoformadustcloud.Ifmechanicalcleaningorincorrectextinguishingworkcausesdustlayerstoformadustcloud,adustexplosioncanbetriggered.Agasorvapourexplosioncanalsoturndustlayersintoadustcloudandthustriggeradustexplosion.Inadditiontothechemicalcharacteristicsofthedust,thefinenessofthesolidparticlesandtheirresultantoverallsurfaceareaandthehumidityalsoplayamajorrole.Thecharacteristicsaredeterminedbyprocessesthattakeplacedirectlyonthesurfaceofthesolid.

4.4. Explosion limits

Anatmospherecanonlybeexplosiveifthegaseouscombustiblematerialispresentataparticularconcentration.Iftheconcentrationistoohigh(richmixture),thematerialcannotaccesssufficientoxygenandanexplosioncannotoccur.Iftheconcentrationistoolow(leanmixture),the combustion cannot spread and it will come to an end. The limits within which an explosion can occur are referred to as the upper explosion limit (UEL) and the lower explosion limit (LEL).ThelimitsandothercharacteristicdataforsubstancesaregivenintheGESTISSubstanceDatabase (www.dguv.de/ifa/GESTIS/GESTIS-Stoffdatenbank/index-2.jsp).If the ambient conditions differ from the atmospheric conditions, the explosion limits are shifted accordingly.Forexample,whentheaircontainsahigherpercentageofoxygen,orwhenpressure is higher, the upper explosion limit is greater.In dust clouds, the average particle size is of crucial importance, in addition to the material characteristics.Greaterfinenessincreasesthetotalsurfaceareaofthedustthatisabletoreactwithoxygen.

Image:Explosionrange

100vol.%

100vol.%

Mixture too rich

Partial combustion, no explosion

Air concentration

Concentrationofflammablesubstance

Explosion range

Explosion limitUpperLower

0vol.%

0vol.%

Mixture too lean

No combustion

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Gases/vapours LEL UEL Hydrogen 4.0% 77.0%Methane 4.4% 17.0%Acetylene 2.3% 100.0%Propane 1.7% 10.8%Carbondisulphide 0.6% 60.0%Hydrogensulphide 4.3% 45.5%Ammonia 15.4% 33.6%Diesel fuel 0.6% 6.5%Petrol 0.6% 8.0%Ethanol 3.1% 27.7%Carbonmonoxide 11.3% 75.6%

Table:Concentrationsofflammablesubstances

4.5. Maximumexperimentalsafegap(MESG)

The maximumexperimentalsafegap(MESG)isameasurementofhoweasilyahotflame willpassthroughanarrowgap.Itisdeterminedbyignitingagasmixtureinatestapparatus anddetermininghowwidea25mm-longgapneedstobeforflamestobeabletopass through it.

Image:Gapvariants

4.6. Minimumignitionenergy,minimumignitioncurrent

Foranexplosivemixturetoignite,aminimumignitionenergymustbepresent,createdbyaspark.Thesparkproducesaveryhightemperaturelocally,theexplosiveatmospherestartstocombustandtheenergythisreleasescausesanexplosion.Theminimum ignition current (MIC) is the minimum amount of current in a circuit that is required for an explosive mixture to ignite, regardless of its composition, relative to the minimum current required to ignite a methane gas mixture.


Gapwidth

GaplengthFlat gap

Cylindrical gap

Threaded gap

Subgroup A and B

Subgroup A, B andC

Subgroup A, B andC

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4.7. Groups

TheexplosivesubstancesaredividedupintogroupsonthebasisoftheirMESGandMICvalues.GasesbelongtoGroup II,withsubgroupAtheleastdangerousandsubgroupCthemost.

Group/subgroup Maximum experimental safegap

Minimum ignition current, relative

II A > 0.9 mm > 0.8II B 0.5 < x < 0.9 mm 0.45<y<0.8IIC < 0.5 mm < 0.45

Table:Groups

DustsareclassifiedintheseparateGroup III. Thisgroupalsocontainssubgroups:

● IIIA:flammablelint ● IIIB:non-conductivedusts ● IIIC:conductivedusts

ThesesubgroupshavenotbeendirectlyadoptedintheATEXdirectives.Thismarkingapplies,however, in conjunction with the harmonised standards EN 60079 and EN 80079.

Althoughtheterm“explosiongroup”wasonceusedwidely,itisnolongerusedinthelatestindustrialstandards.Themoregeneralterm“group”isnowusedinstead.

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5. Temperature classes

To assess the ignition risk of individual substances with greater precision, their ignition temperaturemustbeconsidered.Variousfactorsneedtobetakenintoaccount,suchastheform,size,typeandcharacteristicsofthecontactsurface.Themaximumoccurringsurfacetemperaturemustalwaysbelowerthantheignitiontemperature.

5.1. Gases/vapours

Forgasesandvapours,thespecificignitiontemperatureisdeterminedinaccordancewithEN60079-20-1-Materialcharacteristicsforgasandvapourclassification. Gasesandvapoursareclassifiedbytemperatureclassaccordingly.

Temperature class Ignition temperature range ofmixture

Permissible surfacetemperature ofequipment

T1 >450°C 450°CT2 >300to<450°C 300°CT3 >200to<300°C 200°CT4 >135to<200°C 135°CT5 >100to<135°C 100°CT6 > 85to<100°C 85°C

Table:Temperatureclasses

II A II B IICT1 Methane

Ammonia Carbonmonoxide

Hydrogen

T2 Propane Petrol

Ethanol Acetylene

T3 Diesel HydrogensulphideT4 AcetaldehydeT5T6 Carbondisulphide

Table:Classificationofgasesandvapours

If operation will result in the gas being heated to the temperature of the surrounding surfaces, the surfacetemperaturemustnotexceed80%oftheignitiontemperatureofthegasmixture.Thesurface temperature can rise to the ignition temperature of the gas if the explosive atmosphere onlyoccursbrieflyorrarelyinnormaloperation.


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5.2. Dusts

Flammabledusts,unlikegasesandvapours,arenotclassifiedintemperatureclasses.Thereis,however,astandardisedsystemforcalculatingtheircriticalsurfacetemperature.Thiscalculationmethod is set down in EN 80079-20-2 - Explosive atmospheres: Material characteristics - Combustible dusts test methods and inEN50281-2-1-Testmethods;methodsfordeterminingtheminimumignitiontemperaturesofdustfordustlayers<5mm.Dust can be suspended in the air in the form of a dust cloud or deposited on a surface as a dust layer.Theignitiontemperatureofadustcloudmaybesignificantlydifferentfromthatofadustlayer.Therearedifferentvaluesforthetwoparameters.Todeterminethemaximumpermissiblesurfacetemperature,safetyfactorsneedtobetakenintoaccount.Forastandardiseddustlayerwith a thickness of 5 mm, there must be a difference of 75 K between the ignition temperature and the permissible surface temperature. For a dust cloud, the surface temperature must not exceed 2/3 of the ignition temperature. The lower of these two temperatures must then be taken into account when devices are being selected.TheignitiontemperaturesofdustsandotherspecificcharacteristicsaregivenintheGESTISdust databaseprovidedbyGermany’sInstituteforOccupationalSafetyandHealth(http://staubex.ifa.dguv.de/explosuche.aspx?lang=e).

IgnitiontemperatureofdustsDustlayer:permissiblesurfacetemperature TL perm.=TL min. – 75 K

Dustcloud:permissiblesurfacetemperature TC perm.=2/3TC min.

Max. permissible surface temperature of device TL perm.≥Tperm.≤TC perm.

Table:Ignitiontemperatureofdusts

Dust layers greater than 5 mmThetemperaturecharacteristicsdeterminedaccordingtoEN80079-20-2onlyapplyfordustlayerswithathicknessof5mmorbelow.Thethermalinsulationincreasesinlayerswithgreaterthicknesses.Thismeansthatthedevice’smax.permissiblesurfacetemperatureneedstobereduced further.The temperature is derived from the graph given in EN 60079-14 - Electrical installations design, selection and erection.Forlayerthicknessesexceeding50mm,theignitiontemperatureneedstobedeterminedinlaboratorytests.Thisalsoappliestoalllayerthicknessesexceeding5mmwheretheignitiontemperaturefora5mmthicknessislessthan250°C.Laboratorytestsarealsoneedediftheequipmentisfullycoveredbyalayerofflammabledust.

Determiningthemax.surfacetemperaturefordustlayers>5mm

Max.permissiblesurfacetemperature[°C]

Layerthickness[mm]

≥400°C

≥320°C

≥250°C

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6. Ignition sources

Topreventanexplosioneffectively,itisfirstnecessarytoidentifywhattypesofignitionsourcesarepossibleandwhichonesapplyfortheparticularequipment.EN 1127 - Explosive atmospheres provides an overview of possible ignition sources.

6.1. Hot surfaces

In some cases, the temperature of a surface alone is enough to ignite an explosive atmosphere. Thecriticaltemperatureisdependentonavarietyoffactors.Forexample,theformandthesizeof the heated element, the concentration gradient in the wall area and to some extent even the wallmaterialallplayarole.Hotsurfacessuchasradiators,dryingcabinetsandheatingcoilsareeasytoidentify.Butmechanical procedures and cutting processes can also create hazardous surface temperatures. Thesameappliestodevicesandcomponentsthatconvertmechanicalenergyintoheat,suchasfriction clutches and mechanical brakes. Moving parts in bearings, shaft feed-throughs and sleevescanalsobecomeignitionsourcesiftheyhaveinsufficientlubrication.Dirtorforeignbodiesenteringthedevicecancreatehightemperaturesalmostimmediatelyinsomecases.

6.2. Flames, hot gases and particles

Flames, even in their smallest form, are one of the most effective sources of ignition. Flames generallyoccurincombustionenginesandinanalysisinstruments,andattheirgasoutletpoints.Evenifthereisanexplosiveatmosphereoutsidethedevice–inadjacentpartsofthesystem–flamescanpassthroughopeningssuchasbleedlines,orhotgasesandparticlescanbeblowninto these areas and cause an ignition.

6.3. Mechanicallygeneratedsparks

Mechanicallygeneratedsparksarecreatedwhenparticlesatanelevatedtemperaturebecomedetached from solid materials as a result of friction, impact or grinding. If these particles consist ofoxidisingsubstancessuchasironorsteel,theycanreachtemperaturesfarexceeding1,000°Casaresultoftheoxidationprocess,creatinganignition.Sparkscanalsobecreatedbyforeignbodiessuchasstonesandmetalparticlesenteringrotating devices and components.Impactinvolvingrustorlightmetalssuchasaluminiumandmagnesium,oralloysofthesetwometals,cangenerateathermitereactionwithveryhightemperatures.

6.4. Electrical apparatus

InelectricalequipmentsuchasI&ECdevices(instrumentationandcontrolengineeringdevices)andmotors,electricalsparks(suchasthosecausedbyelectricalcircuitsopeningorclosing,looseconnectionsorcompensatingcurrents)canfunctionasignitionsourcesevenatlowvoltages.


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6.5. Strayelectriccurrents,cathodiccorrosionprotection

Disconnecting,connectingorbypassingsystemsorsystempartsinwhichcompensatingcurrentscan occur can create electrical sparks even at low potential differences. Even if no sparks occur, currentpathsmayheatuptocriticallevels.The above-mentioned ignition hazards can also be expected when cathodic corrosion protection isusedwithanexternalpowersupply.Ifsacrificialanodesareused,however,ignitionhazardsresultingfromsparkformationarenotgenerallytobeexpected.

6.6. Staticelectricity

Unlikedischargeinthecaseofstrayelectriccurrents,adischargeresultingfromstaticelectricitycan occur even if no voltage source is present. This means that there is a risk of spark formation resultingfromstaticdischargeeveninnon-electricalsystemsandsystemparts.Plasticsmadefrom non-conductive materials can become charged. Separatingprocessessuchasafilmpassingoverarollerorhydraulicoilflowingoverfilterelements can result in discharge and sparks.

6.7. Lightning

Becauseofthelargeamountofenergyinvolved,lightningalwayscausesanexplosiveatmospheretoignite.Strongcurrentsflyinalldirectionsaroundtheimpactpointthatcancauseignitablesparksandfirespraysintheadjacentareas.Thecurrentsthatoccurcanalsocreateintenseheatingofthelightning’sdischargechannels.

6.8. High-frequencyelectromagneticwaves (radiowaves,microwaves;frequency:104 Hz–3*1011Hz)

Systemsthatreleasehigh-frequencyelectromagneticwavesareforexamplehigh-frequencygeneratorsforheating,drying,curingandwelding.Conductivepartsinthistypeofradiationfieldact as receivers and can ignite an explosive atmosphere under certain conditions. This can cause thin wires to glow with heat.

6.9. Electromagnetic waves (infraredtoUVradiation;frequency:3*1011 Hz–3*1015Hz)

Radiationinthisspectralrangecanbecomeasourceofignition,especiallywhenfocused,orstartafireonsolidsurfacesasaresultofabsorption.Inlaserradiationinparticular,thepowerdensitycanbesufficienttocauseignitionevenfromagreatdistance.Sunlightcantriggeranignitioniftheradiationisconcentratedbyobjectssuchasbottlesorconcavemirrors.Insomecases,theradiationfromstronglightsourcescanbeabsorbedbydustparticlessogreatlythattheparticlesbecomeignitionsources.

6.10. Ionising radiation

IonisingradiationcausedbyX-raytubesorradioactivesubstancescanigniteanexplosiveatmosphereasaresultofenergyabsorption.However,theradiationsourcecanalsoheatupenough to be considered an ignition source itself.Ionising radiation can also cause chemical mixtures to decompose and reactive radicals or chemicallyvolatilecompoundstobereleased.Thiscanresultinignition.

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6.11.Ultrasound

Whenultrasoundisapplied,thetreatedsubstanceabsorbstheenergy,whichcancauseittoheat up enough to generate an ignition.

6.12.Adiabaticcompression,shockwaves,flowinggases

An abrupt compression of a shock wave can cause an increase in temperature. This temperature increase can be large enough to cause an explosive atmosphere to ignite.Flowing gases can cause a temperature increase that can lead to ignition when high-pressure gasesinthepipesystemaresuddenlydepressurisedatnarrowpoints,bendsorclosedgatevalves,causingshockwavestobediffractedorreflected.

6.13. Exothermic reactions

Certainunstablesubstancestendtochemicallyreactevenatroomtemperature.Thisreleasesheat,whichisnormallydirectlytransferredtothesurroundingareawithoutcausinganyincreaseinthesubstance’stemperature.Ifanythingpreventsthisenergytransferfrombeingcompletedinfull, the substance can self-ignite. This can also happen if the substance is stored at an excess temperature.Thesesubstancescanbeeithergasmixturesordusts(oxidation).

7. Classificationandcategorisationofequipment forexplosiveatmospheres

“Equipment”meansmachines,apparatus,fixedormobiledevices,controlcomponentsandinstrumentationthereofanddetectionorpreventionsystemswhich,separatelyorjointly,areintendedforthegeneration,transfer,storage,measurement,controlandconversionofenergyand the processing of material which are capable of causing an explosion through their own potential sources of ignition.

7.1. Equipmentgroupsasdefinedby2014/34/EU

EquipmentgroupIEquipmentgroupIonlyincludesequipmentintendedforuseinundergroundpartsofmines,andinthosepartsofsurfaceinstallationsofsuchmines,liabletobeendangeredbyfiredampand/orcombustibledust.EUDirective2014/34/EUdividesthisgroupupintotheequipmentcategoriesM1 and M2.The M stands for miningandthenumbersignifiesthesafetylevel.M1 indicates a very high level ofsafety.Thismeansthatoperationoftheequipmentcancontinueinanexplosiveatmosphereevenifequipmentdisturbancesoccurrarely.Ifonemeansofprotectionfails,asecondindependentmeansofprotectionthenprovidestherequiredlevelofsafety.Furthermore,safetyisstillassurediftwofaultsoccurindependentlyofeachother.M2 indicates a highlevelofsafety.Theequipmentassuressafetyinnormaloperationunderthesevereoperatingconditionsinmining.Intheeventofanexplosiveatmosphereoccurring,thisequipmentisswitchedoffsecurely.EquipmentgroupIIEquipmentinequipmentgroupIIcanbeusedinallareas(apartfrommining)inwhichanexplosiveatmosphere constituting a mixture of air and gases, vapours or mists and/or air/dust mixtures is to be expected.


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7.2. Equipment categories

DevicesofequipmentgroupIIareclassifiedintooneofthe3equipmentcategories,basedonthefrequencyanddurationofanexplosiveatmosphereandtherequiredlevelofsafety.

● Equipmentcategory1 Areasofapplicationforthiscategoryareareasinwhichanexplosiveatmosphereconstitutingamixtureofairandgases,vapoursormistsorair/dustmixturesispresentcontinuouslyorforlongperiodsorfrequently.Thisequipmentprovidesaveryhighlevelofsafetyeveninthecaseofrareequipmentdisturbances.AsisthecaseforcategoryM1,ifonemeansofprotectionfails, a second independent means of protection must be present, and if two faults occur independentlyofeachothertherequiredlevelofsafetymuststillbeprovided.

● Equipmentcategory2 Equipmentinthiscategoryisintendedforuseinareasinwhichanexplosiveatmospherecomprisedofgases,vapours,mistsordust/airmixturescanbeexpectedtooccuroccasionally.Thisequipmentprovidesahighlevelofsafetyinnormaloperationandintheeventoffrequentdisturbances and foreseeable faults.

● Equipmentcategory3 Equipmentincategory3isintendedforuseinareasinwhichanexplosiveatmospherecomprised of gases, vapours, mists or dust clouds is not to be expected, or, if such an atmospheredoesoccur,itislikelytodosoonlyinfrequentlyandforashortperiod.Equipmentinthiscategoryprovidestherequiredlevelofsafetyinnormaloperation.

7.3. Typesofexplosiveatmosphere

Explosiveatmospheresaredividedupintoatmospherescausedbygasandatmospherescausedbydust.Accordingly,thelettersG and D are used for marking. Fluids do not pose an explosion hazard in themselves, but the vapour/air mixtures that form at their surfaces do. Areas containinghazardousfluidsarethereforealwaystreatedasgas-basedatmospheres.

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7.4. Zonedivisionsasdefinedbydirective1999/92/EC

Thisdirectivedefinesexplosiveareasasparticularzonesaccordingtothefrequencyandduration of an explosive atmosphere. Equipment can be designed in accordance with the particular zones. This approach makes sense from an economic perspective, without neglecting theissueofsafety.

● Zone 0 (gas) Locationinwhichanexplosiveatmosphereconsistingofamixturewithairandflammablegases,vapoursormistsispresentcontinuously,orforlongperiodsorfrequently.Thisonlyincludessmallareasinworkplacesthataremostlyinaccessibleorinternalpartsoftechnologicalsystems.

● Zone 1 (gas) Locationinwhichanexplosiveatmosphereconsistingofamixturewithairandflammablegases,vapoursormistislikelytooccurinnormaloperationoccasionally.Thiszoneincludestheclosesurroundingsofzone0.Thepreciselimitsmustbedefinedinaccordancewiththeparticular hazardous substance and the ambient conditions.

● Zone 2 (gas) Locationinwhichanexplosiveatmosphereconsistingofamixturewithairandflammablegases,vapoursormistisnotlikelytooccurinnormaloperation,butifitdoesoccur,willpersistforashortperiodonly.

Image:Zonedivisionsforgases

Pit

Zone 2 Danger rare and brief

Zone 1

Zone 2Zone 2 Pump stationZone 1

To process

Zone 1 Danger occasionalZone 0 Danger continuous, long-term or frequent

Tank Zone 0

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● Zone 20 (dust) Locationinwhichanexplosiveatmosphereintheformofacloudorlayerofcombustibledustinairispresentcontinuously,orforlongperiodsorfrequently.Thisonlyincludessmallareasinworkplacesthataremostlyinaccessibleorinternalpartsoftechnologicalsystems.

● Zone 21 (dust) Locationinwhichanexplosiveatmosphereintheformofacloudorlayerofcombustibledustislikelytooccurinnormaloperationoccasionally.Thiszoneincludesareasthatcontaindustdepositslargeenoughfordustcloudstooccuroccasionallyinnormaloperation.

● Zone 22 (dust) Locationinwhichanexplosiveatmosphereintheformofacloudorlayerofcombustibledustinairisnotlikelytooccur,butifitdoesoccur,willpersistforashortperiodonly(e.g.inthecaseofdisruptions).Dustdepositsintheseareasmustberemovedregularly.

Image:Zonedivisionsfordusts

Theterms“continuously”,“occasionally”,“longperiods”and“shortperiods”arenotdefinedpreciselyinthesedirectives.Referencevaluesforclassificationaregiveninthetablebelow.

ZoneFrequencyofoccurrenceofmixtures Period

(duration)Annually Day/month/year0 20 > 1,000 times >3times/day > 10 h

1 21

> 10 times < 1,000 times

> 1 time/month <3times/day > 30 min

2 22

> 1 time < 10 times

>1time/year < 1 time/month < 30 min

Table:Frequencyofoccurrenceofmixtures

Zone 22 Danger rare and briefZone 21 Danger occasionalZone 20 Danger continuous, long-term or frequent

Hydraulic conveying

Filling line

Zone 20

Zone 22

SiloZone21

Explosion door

Carbon dust silo

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7.5. Criteriafortheselectionofequipmentandprotectivesystems

If the explosion protection document based on a risk assessment does not state otherwise, equipmentandprotectivesystemsforallplacesinwhichexplosiveatmospheresmayoccurmustbeselectedonthebasisofthecategoriessetoutinDirective2014/34/EU.Fortheindividualzones,equipmentcanbeusedasshowninthetablebelow,providedtheyaresuitableforgases,vapoursormistsand/ordusts:

Zone Equipmentcategory0 20 1

1 21 1 or 2

2 22 1, 2 or 3

Table:Zones–equipmentcategories

8. Equipmentprotectionlevel

Asanalternativetothecategorisationofexplosion-protecteddevicesdefinedbyEUDirective2014/34/EU,theconceptofequipmentprotectionlevel(ELP) has been introduced at an international level.It uses the divisions M (mining), G (gas) and D (dust), in accordance with the particular explosive atmosphere. The letter a, b or cisaddedtoindicatethelevelofprotection.Onlytwoprotectionlevelsapplyformining:a and b. The relationship between the equipment protection levelandthecategoriesoftheATEXDirectiveisshowninthefollowingtable:

Equipmentprotec-tion levelEPL

ATEX Directive 2014/34/EU category

ATEX Directive 99/92/EC zone

Protection provided

Ma I M1 - VeryhighMb I M2 - HighGa II1G 0 VeryhighGb II2G 1 HighGc II3G 2 NormalDa II 1D 20 VeryhighDb II 2D 21 HighDc II 3D 22 Normal

Table:EquipmentprotectionlevelEPL

ThestandardEN60079-14specifiesparticularignitionprotectiontypesforeachEPL.Theprotectionlevelsa,bandcarealsousedforsomeoftheignitionprotectiontypes(e.g.ignitionprotectiontype“intrinsicsafety”–ia,ib,ic–seealsosection9).


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9. Typesofignitionprotection

If all measures to prevent an explosive atmosphere from occurring have been taken and an explosiveatmosphereneverthelessoccurs,onlyexplosion-protectedequipmentmaybeusedforthe affected area.Electricalequipmentcanbedividedupintovariousignitionprotectiontypesasdefinedintheconstruction provisions of the series of standards EN 60079 - Explosive atmospheres.

Zone EPL Ignition protection type Code Standards

0 Ga

Flameproof enclosure da EN 60079-1Intrinsicsafety ia EN 60079-11Encapsulation ma EN 60079-18Two independent ignition protection typesthatbothfulfilEPLGb - EN 60079-26

Protection of equipment and transmissionsystems using optical radiation

op is EN 60079-28

1 Gb

Flameproof enclosure db EN 60079-1Increasedsafety eb EN 60079-7Intrinsicsafety ib EN 60079-11Encapsulation mb EN 60079-18Liquid immersion ob EN 60079-6

Pressurised enclosure pxb pyb EN 60079-2

Powderfilling q EN 60079-5Protection of equipment and transmissionsystems using optical radiation

op is op sh op pr

EN 60079-28

2 Gc

Flameproof enclosure dc EN 60079-1Intrinsicsafety ic EN 60079-11Encapsulation mc EN 60079-18Liquid immersion oc EN 60079-6Non-sparking nA EN 60079-15Restricted breathing nR EN 60079-15Non-incendive nC EN 60079-15Increasedsafety ec EN 60079-7Pressurised enclosure pzc EN 60079-2Protection of equipment and transmissionsystems using optical radiation

op is op sh op pr

EN 60079-28

Table:Electricalignitionprotectiontypesforgas–protectionprovided

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20 DaIntrinsicsafety ia EN 60079-11Encapsulation ma EN 60079-18Protectionbyenclosure ta EN 60079-31

21 Db

Intrinsicsafety ib EN 60079-11Encapsulation mb EN 60079-18Protectionbyenclosure tb EN 60079-31Pressurised enclosure pxb,pyb EN 60079-2

22 Dc

Intrinsicsafety ic EN 60079-11Encapsulation mc EN 60079-18Protectionbyenclosure tc EN 60079-31Pressurised enclosure pzc EN 60079-2

Table:Electricalignitionprotectiontypesfordust–protectionprovided

Non-electricaldevicesareprimarilydescribedbytheinternationalstandardsEN 80079-36 and EN80079-37-Non-electricalequipmentforexplosiveatmospheres. The previous standard partsforconstructionalsafety"c",controlofignitionsources"b"andliquidimmersion"k"werecombined in standard EN 80079-37. In addition, a few standards from the EN 13463 series apply.


0 20

Ga Da

Constructionalsafety cEN 80079-37Liquid immersion k

Controlofignitionsource b

1 21

Gb Db


Controlofignitionsource bFlameproof enclosure d EN 13463-3Pressurised enclosure p EN 60079-2

2 22

Gc Dc


Controlofignitionsource bFlameproof enclosure d EN 13463-3Pressurised enclosure p EN 60079-2Flow restricting enclosure fr EN 13463-2

Table:Non-electricalignitionprotectiontypes-protectionprovided


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9.1. Flameproof enclosure, electrical ignition protection

Standard: EN60079-1-Equipmentprotectionbyflameproofenclosures“d”Code: da, db, dcAreaof application:

Zone 0, 1, 2

● Principle: Partsthatcouldigniteapotentiallyexplosiveatmospherearelocatedinsideanenclosurewhich can withstand the pressure of an explosion of the explosive mixture inside, and prevent the transmission of the explosion to the explosive atmosphere surrounding the enclosure. This principle allows an explosive atmosphere to penetrate into the housing of the equipment. If an explosion occurs inside the housing, this explosion must not be transferred to the surroundingarea.Anygapspresentinthehousingmustthereforebedesigned,intermsoftheirgeometryandlength,tosecurelypreventignitionoutsideofthehousing.Theexplosionpressurethatdevelopsinsidethehousingmustbesecurelycontrolledbythehousing.

● Applications: Equipment that produces sparks or electric arcs and/or hot parts during operation. Switchingdevicesandswitchingsystems,commandanddisplayunits,controls,motors,transformers, heating devices, lights Solenoid valves, proportional and servo valves

9.2. Pressurised enclosure

Standard: EN60079-2-Equipmentprotectionbypressurizedenclosure“p”Code: pxb,pyb,pzcAreaof application:

Zone 1, 2, 21, 22

● Principle: Anexplosiveatmosphereispreventedfromdevelopinginsidetheequipmentbyanignition protection gas inside the enclosure being kept at a higher pressure than that of the surrounding atmosphere. Theignitionprotectionisdividedupintothreeignitionprotectiontypes(px,pyandpz),dependingontherequiredequipmentprotectionlevel(GborGc)andonwhetherthehousingcontainsanyignitableequipment.Foruseinzone2or22,theover-pressureprovidedbytheprotectivegasmustbeatleast25Pafortheignitionprotectiontypepz.Fortheignitionprotectiontypespxandpyforuseinzone1or21,theover-pressuremustbeatleast50Pa.Beforestart-up,thehousingandallthecorrespondingpipesmustbeflushedthoroughly.During operation, the over-pressure must be monitored and if it drops, a warning must be issuedorthedevicemustbeshutdown.Conditioneddriedcompressedairisnormallyusedastheprotectivegas.NitrogenorCO2 can also be used as an alternative.

● Applications: Equipment that produces sparks or electric arcs and/or hot parts during operation. Switchgearandcontrolcabinets,analysisinstruments,largemotors

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9.3. Powderfilling

Standard: EN60079-5-Equipmentprotectionbypowderfilling“q”Code: qAreaof application:

Zone 1, 2

● Principle: Thehousingisfilledwithafinelygrainedfillingmaterialtopreventanelectricarcthatdevelopsinside the housing from igniting an explosive atmosphere surrounding the housing when the equipmentisusedasintended.Theremustbenoriskofignitionbyflames,orbyincreasedtemperatures, at the surface of the enclosure. Thehousingisfilledwithquartzsandorelsewithglassballs.Thegrainsize,purity,residualmoistureanddielectricstrengthmustmeetparticularcriteria.Thehousingsmustbefilled,closed up and sealed during manufacture. It must not be possible to open them without leavingvisiblesigns;afterrepairwork,thehousingsmustbesealedandlabelledagain.

● Applications: Componentsthatproducesparksorhotpartsthatcanfunctionperfectlywhenfilledwithafinelygrainedfillingmaterial. Sensors,displayunits,electronicballasts,transmitters

9.4. Liquid immersion, electrical ignition protection

Standard: EN60079-6-Equipmentprotectionbyliquidimmersion“o”Code: ob, ocAreaof application:

Zone 1, 2

● Principle: Partsthatcouldcauseanexplosiveatmospheretoigniteareimmersedinaprotectivefluidsuch that an explosive atmosphere above the surface of the liquid or outside the encapsulated area cannot be ignited. Componentsthatconstituteanignitionsourceareimmersedintheprotectivefluiddeeplyenoughtopreventignitionspreadingtotheareaabovethesurfaceofthefluid.Thefluidlevelmustbemonitored.Itmustbeensuredthattheprotectivefluiddoesnotheatuptoprohibitedlevels.Thefluidqualitymustbemonitoredasitscharacteristicscouldchangeasaresultoftime deterioration or electric arc or sparks could cause it to decompose.

● Applications: Transformers, starting resistors


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9.5. Increasedsafety

Standard: EN60079-7-Equipmentprotectionbyincreasedsafety“e”Code: eb, ecAreaof application:

Zone 1, 2

● Principle: Additionalmeasuresaretakentoachieveanincreasedlevelofsafetysuchthatexcesstemperatures and the formation of sparks or electric arcs in the internal and external parts of equipment cannot occur during normal operation. Electricalconnectionsmustbedesignedtopreventthesupplylinesfrombecomingreleasedfromtheintendedpositionduringclampingandtheymustbesecuredagainstbecomingloose. The contact pressure must also be maintained in the long term under the foreseen temperature changes. As there is some risk of an explosive gas mixture penetrating, all surfaces inside the housing must also be prevented from reaching excess temperatures. The housing undergoes a mechanical impact test and minimum requirements for the IP protection classapplyinaccordancewithhowthehousingisused. Therequirementsfromtheignitionprotectiontype"nA"(EN60079-15)weretransferredtothisstandardandarenowmarkedas"ec".

● Applications: Terminals and terminal boxes, control boxes for installing Ex components, squirrel cage motors, lights Solenoid valves, proportional and servo valves

9.6. Intrinsicsafety

Standard: EN60079-11-Equipmentprotectionbyintrinsicsafety“i”Code: ia, ib, icAreaof application:

Zone 0, 1, 2, 20, 21, 22

● Principle: Intrinsicallysafeelectricalequipmentcontainsonlycircuitswhichmeettherequirementsofintrinsicallysafecircuits.Acircuitisintrinsicallysafeifnoneofthesparksorthermaleffectsthatoccurunderthetestconditionsspecifiedinthestandardcouldcauseanexplosiveatmosphere to ignite. The test conditions cover both normal operation and certain fault conditions. The equipment is divided up into the subgroups ia, ib and ic depending on the zone in which itistobeused.Allconstructionelementsareconfiguredintermsoftheirvoltageandcurrenttoensurethattheenergycontentofthecircuitisnotnormallysufficienttoigniteanexplosivemixture.Energystoragedevicessuchascapacitorsareonlypermissibleinintrinsicallysafecircuitstoaverylimiteddegree. Ifseveralintrinsicallysafepiecesofequipmentareinterconnected,itmustbecheckedthatalltheconstructionelementsasawholestillmeetthecriteriaforintrinsicsafety.ThecorrespondingspecificationsaregiveninEN60079-25.

● Applications: Measuring, monitoring and information devices, sensors and visual or acoustic actuators Solenoid valves, servo valves

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9.7. Ignitionprotectiontype“n_”

Standard: EN60079-15-Equipmentprotectionbytypeofprotection“n”Code: nA,nC,nRAreaof application:

Zone 2

● Principle: Electrical equipment is not able to ignite a surrounding explosive atmosphere in normal operation and under certain abnormal operating conditions.

– nA:non-sparkingequipment Thedesignreliablypreventstheformationofexcesstemperaturesandsparksorelectricarcs in normal operation.

– nC: sealed device The design prevents an external explosive atmosphere from entering. The device cannot be opened in normal operation. It must not be possible for elastic seals to become damaged under normal operating conditions.

– nC: hermetically sealed device The design prevents an external explosive atmosphere from entering. The seal is created byameltingprocesssuchassolderingorwelding.

– nC:non-incendiveequipment Componentwithcontactsthatcloseoropenacircuitthatmaycauseignition.Thecontactmechanism is designed to prevent an explosive mixture from igniting.

– nC: encapsulated device An encapsulation, such as a sealing compound, prevents the external atmosphere from entering the component. The device cannot be opened in normal operation.

– nR: restricted breathing The housing is designed to limit the penetration of gases, vapours and mists. The seal can beprovidedbyencapsulatedsealsorelasticseals.Afterinstallationandmaintenance,itmustbepossibletochecktheimpermeability.Intermsofitspowerdissipation,theequipment must be designed to prevent the surface temperature measured on the outside from exceeding the permissible temperature class. If the component contains parts that produce sparks, the temperature increase must not exceed 10 K in comparison with the ambient temperature.

● Applications: Installation material, terminal compartments, lights, cells and batteries, transformers, contact systems,coilsofsolenoidvalvesormotors,completecircuitboards,spark-generatingequipment,switchingdevices,measuring,monitoringandinformationsystems


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9.8. Encapsulation

Standard: EN60079-18-Equipmentprotectionbyencapsulation“m”Code: ma, mb, mcAreaof application:

Zone 0, 1, 2, 20, 21, 22

● Principle: Partsthatcouldigniteanexplosiveatmospherebysparksorheatingareembeddedina casting compound such that the explosive atmosphere cannot be ignited. Duromers, thermoplastics,elastomerswithorwithoutfillermaterialsandotheradditivescanbeusedascasting compound. The compound must be resistant to electrical, thermal, mechanical and chemicalinfluences.

● Applications: Relays,signallingandcommanddevices,solenoidvalves,motors

9.9. Optical radiation

Standard: EN 60079-28 - Protection of equipment and transmission systemsusingopticalradiation

Code: op is, op pr, op shAreaof application:

Zone 0, 1, 2

● Principle: Appropriate measures are taken to prevent optical radiation from igniting an explosive atmosphere.

– opis:inherentlysafeopticalradiation Undernormalconditionsandcertainfaultconditions,visibleradiationorinfraredradiationcannotsupplyenoughenergytoigniteanexplosiveatmosphere.Inthisprotectionclass,fibreopticalcablescanbedisconnectedandconnectedduringoperation.

– op pr: protected optical radiation Theradiationisenclosedinanopticalfibreorothertransmissionmedium.Fibreopticcablesmustbeconfiguredwithcorrespondingstrength.Equipmentmustbedesignedtopreventahazardousamountoflightenergyfromescaping.

– op sh: optical radiation with interlock Thisprotectionclassinvolvesinterlockshut-offdevicesthatsecurelystoptheopticalradiation in the event of a fault.

● Applications: Fibre optic cables, lamps, lasers, LEDs

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9.10.Protectionbyenclosure

IPXX

Standard: EN60079-31-Equipmentdustignitionprotectionbyenclosure“t”Code: ta, tb, tcAreaof application:

Zone 20, 21, 22

● Principle: Thehousingisimpermeablesuchthatdustpenetrationisprevented(IP6X)orreducedtoanon-hazardouslevel(IP5X).Thetemperatureofthehousingmustnotbeabletoignitethesurroundingatmosphere.Itisessentialthatperfectimpermeabilityisprovided.Theinspectionmustthereforealsoincludeapressuretest.Thisensuresthatanypressuredifferencesthatmayoccurbetweentheinsideandoutside,forexampleasaresultoftemperaturefluctuations,donothaveanynegativeeffectsontheseals.

● Applications: Switchingdevicesandswitchingsystems,control,connectionandterminalboxes,motors,lights Solenoid valves, proportional and servo valves, measuring and monitoring devices

9.11. Flow restricting enclosure

Standard: EN13463-2-Protectionbyflowrestrictingenclosure“fr”Code: frAreaof application:

Zone 2, 22

● Principle: Theimpermeabilityofthehousingpreventsahazardousatmospherefromenteringsuchthatno explosive atmosphere can occur inside the housing. Pressure differences between the innerandouteratmosphere,suchasthosecausedbytemperaturechanges,mustbetakeninto account.

● Applications: Switching devices, complex machines, large machines


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9.12. Flameproof enclosure, non-electrical ignition protection

Standard: EN13463-3-Protectionbyflameproofenclosure“d”Code: dAreaof application:

Zone 1, 2, 21, 22

● Principle: Partsthatcouldigniteapotentiallyexplosiveatmospherearelocatedinsideanenclosurewhich can withstand the pressure of an explosion of the explosive mixture inside, and prevent the transmission of the explosion to the explosive atmosphere surrounding the enclosure. This principle allows an explosive atmosphere to penetrate into the housing of the equipment. If an explosion occurs inside the housing, this explosion must not be transferred to the surroundingarea.Anygapspresentinthehousingmustthereforebedesigned,intermsoftheirgeometryandlength,tosecurelypreventignitionoutsideofthehousing.Theexplosionpressurethatdevelopsinsidethehousingmustbesecurelycontrolledbythehousing. Thedesignrequirementsfornon-electricaldevicesspecifiedbythisstandard, EN13463-3,arelargelyidenticaltotherequirementssetdownbythestandard EN 60079-1 for electrical devices.

● Applications: Brakes,frictionclutches,catalyticconverters

9.13.Constructionalsafety

Standard: EN80079-37-Protectionbyconstructionalsafety“c”Code: hAreaof application:

0, 1, 2, 20, 21, 22

● Principle: Establishedtechnicalprinciplesareappliedtoreducetoaverylowleveltheriskofmechanicalfaults that could result in temperatures or sparks capable of causing ignition. Thecomponentsmustbeconfiguredsuchthatthereisnoriskofheatingasaresultoffriction,for example. The components must also not cause electrostatic charging or friction sparks.

● Applications: Couplings,pumps,geardrives,chaindrives,conveyorbelts,pressureandflow-controlvalves,cylinders,directionalvalves

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9.14.Controlofignitionsource

°CStandard: EN80079-37-Protectionbycontrolofignitionsource“b”Code: hAreaof application:

Zone 0, 1, 2, 20, 21, 22

● Principle: In non-electrical devices, which do not show an effective source of ignition during normal operation, a fault can result in a potential source of ignition. For this reason, often sensors are fittedtothedevices,whichmonitortheproperfunctioningandtriggertherequiredmeasuresasspecifiedbytheoperatingparametersincaseofdeviations. Fortheprotectionclass,theentireignitionprotectionsystem,consistingofasensor,evaluationunitandanoutputdevice,mustbesubjectedtoanassessmentofreliability.ThefunctionalsafetystandardsEN13849orEN61508canbereferredtoforthis.

● Applications: Bearings, pumps, agitators, fans, vacuum pumps

9.15. Liquid immersion, non-electrical ignition protection

Standard: EN80079-37-Protectionbyliquidimmersion“k”Code: hAreaof application:

Zone 0, 1, 2, 20, 21, 22

● Principle: Non-electricaldevicesofthisignitionprotectiontypehavepotentialignitionsourcesthatarerenderedineffectiveeitherbyimmersioninaprotectivefluidorbyconstantwettingwithaprotectivefluidfilm. Unlikeliquidimmersion“o”accordingtoEN60079-6,theliquidimmersionfornon-electricalequipmentcanalsoinvolveelectricallyconductivefluids.

● Applications: Immersionpumps,oil-filleddrivinggears,fluidcouplings


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9.16.Typesofignitionprotection-Mining

IntheareaofGroupI-Mining,onlyselectedignitionprotectiontypesmaybeapplied.Duetotheongoing revisions of the standard series 60079 and 80079, and due to the increasing use of the EPLinthestandards,theclassificationhasnowbecomeeasier.

EPL Ignition protection type Code Standards

Ma

Intrinsicsafety ia EN 60079-11Encapsulation ma EN 60079-18Optical radiation op is EN 60079-28Two independent ignition protection typesthatbothfulfilEPLMb - EN 80079-36

Mb

Flameproof enclosure d EN 60079-1Pressurised enclosure px EN 60079-2Powderfilling q EN 60079-5Increasedsafety eb EN 60079-7Intrinsicsafety ib EN 60079-11Encapsulation mb EN 60079-18Optical radiation op is, op sh, op pr EN 60079-28Constructionalsafety c

EN 80079-37Liquid immersion kControlofignitionsource b

Table:Miningignitionprotectiontypes–protectionprovided

10. Marking

10.1.ATEXDirective2014/34/EU

ProductscoveredbytheATEXDirectivearegivenaCEmarking.Theyarealsogivenaspecialexplosion-protectionmarkingandmarkedwiththeirequipmentgroupandcategory.Example:

II 2 G

Equipment group II (Seepoint7.1)Equipmentcategory2 (Seepoint7.2)Typeofex.atmosphereG (Seepoint7.3)

Ifanotifiedbodyisinvolvedintheconformityprocess,thisbody’sIDnumberisgivennexttotheCEmarking.ThemarkingisthesameasthatofthepreviousDirective94/9/EC.

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10.2. Marking according to standards requirements

ThedirectivemarkingisfollowedbymarkinginaccordancewiththestandardsEN60079forelectrical devices and EN 80079-36 for non-electrical devices. This involves additional markings indicating the protection classes and area of application.Exampleofelectricalequipmentforareasatriskofgasexplosion:

II1G Ex ia IIC T6 Ga

SymbolExIgnitionprotectiontypei protection level a (Seepoint9.6)GroupII(gas)C (Seepoint4.7)Temperature class T6 (Seepoint5.1)Equipmentprotectionlevel(EPL)Ga (Seepoint8)

Exampleofelectricalequipmentforareasatriskofdustexplosion:

II 2 D Ex tb IIIC T80 °C Db

SymbolExIgnitionprotectiontypet protection level b (Seepoint9.10)GroupIII(dust)C (Seepoint4.7)Temperature class T80 °C (Seepoint5.2)Equipmentprotectionlevel(EPL)Db (Seepoint8)

Exampleofnon-electricalequipmentforareasatriskofgasexplosion:

II2G Ex h IIC T6 Gb

SymbolExIgnitionprotectiontypeh (seepoint9.13-9.15)GroupII(gas)C (Seepoint4.7)Temperature class T6 (Seepoint5.1)Equipmentprotectionlevel(EPL)Gb (Seepoint8)

10.3. Markings for special conditions

If a piece of equipment is to be used in special conditions or conditions that differ from the standards, this is indicated with an additional marking. The letter X, for example, indicates differing ambient temperatures or special installation conditions. The special conditions should be indicated on the device wherever possible, and alwaysindicatedintheoperatingmanual.Componentsthatareusedinconjunctionwithothercomponentsordevicesratherthanontheirown are marked with U.Theseincompletecomponentsmustbeincludedinthecertificationofthe corresponding device.


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600

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8

Dev

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with

op

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atio

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EN

600

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tion

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2.Equ

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roup

s

Equipm

entg

roup

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quip

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t int

ende

d fo

r use

in u

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grou

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nd in

thos

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rts o

f sur

face

inst

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of s

uch

mines,liabletobeendangeredbyfiredam

pand/orcom

-bu

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ust

Equipm

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roup

II:

Equ

ipm

ent i

nten

ded

for u

se in

oth

er a

reas

that

cou

ld b

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ris

k of

an

expl

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mos

pher

e

4.Typesofexplosiveatm

osph

ere

G (g

as):

Mix

ture

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ases

, vap

ours

or m

ists

and

air

D (d

ust):

Dus

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estrictio

nsfo

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ipment

X:

indicatesspecialconditions

U:

Excomponentwithsub-certification,

no

t to

be u

sed

on it

s ow

n

3.Equ

ipmentcategories

Equipm

entcategoryM1:

Mining–veryhighlevelofsafety

Equipm

entcategoryM2:

Mining–highlevelofsafety

Equipm

entcategory1:

Veryhighlevelofsafety

Equipm

entcategory2:

Highlevelofsafety

Equipm

entcategory3:

Normallevelofsafety

5. EX s

ymbo

l

9.Equ

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rotectionlevel(EP

L)

EPL

Category/typeofatm

osph

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Ma

M1

Mb

M2

Ga

1G

Gb

2G

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3G

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1 D

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s

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II A

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cl

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135

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85

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ust e

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rea

the

max

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face

tem

pera

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tate

d directly

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alequ

ipment

Electricalequ

ipment

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11. Explosion protection worldwide and the legal situation

Overtheyears,almosteverysinglecountryhasissueditsownsetofrulesforexplosionprotection.Inthecontextofglobalisation,however,nationalspecificationsandidiosyncrasiestend to function as a trade barrier. To counter this, initiatives were set up some time ago to harmonisetheguidelinesforexplosionprotection.WithinintheEuropeanUnion,thishasalreadybeenachievedbytheATEXDirectives.ThereisasimilardirectivefortheEurasianCustomsUnion.Ataninternationallevel,theIECExschemehasbeensetupbytheIEC (International Electrotechnical Commission).Countries,suchastheUSandCanada,BrazilorKorea,havetheirowndirectives.Therearealreadysignshowever,thatapprovalsissuedonthebasisoftheIECExschemecouldbeexpandedfastertonationalcertificatesinthesecountries.

11.1. Europe – ATEX Directives

TheEUhasissuedtwoharmoniseddirectivesforEuroperelatingtohealthandsafety.

● Requirementsformachineryandequipment Directive 2014/34/EU of the European Parliament on the harmonisation of the laws of the MemberStatesconcerningequipmentandprotectivesystemsforuseinpotentiallyexplosiveatmospheres. This directive governs the use of both electrical equipment and non-electrical equipmentinpotentiallyexplosiveareas.Itismainlytargetedtowardsthemanufacturersofequipmentandcomponentsthataretobeusedinpotentiallyexplosiveareas.ItreplacedthefirstATEXdirective94/9/EC.Asof20April2016,allnewproductslaunchedonthemarketmustbecertifiedinaccordancewiththenewDirective2014/34/EU.AllcertificatesissuedunderDirective94/9/ECwillremainvalid,however. TheATEXdirectivereferstoarticle114oftheEUTreatyonfreemovementofgoods(LisbonTreaty).ThisiswhythedirectiveissometimesalsocalledATEX114.Inolderdocuments,thenameATEX95isused(article95oftheECMaastrichtTreaty).

● Requirementsforthesystembuilder/owner Directive 99/92/EC(ATEX153)definestheminimumrequirementsforhealthandsafetyin workplaces, for operating conditions and for the handling of products and materials in potentiallyexplosiveatmospheres.Thedirectivedividesuptheworkplaceintozonesanddefinescriteriaforcategorisingtheproductsinsidethesezones.

● Transposition into national law ThedirectiveshavebeentransposedintonationallawinthecountriesoftheEuropeanUnion.


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11.2.Internationalrules–lECEx

TheIECpublishesgloballystandardisedregulationsforelectricaltechnologyandelectronics.Technical committees compile the standards for the various specialist areas. To ensure harmonisation,thestandardspublishedbytheIECaremainlyadoptedinnationalandEuropeanstandardswithoutanymajorchangesmade.IECpublicationsconcerningtheexplosionprotectionofelectricaldevicesandsystemsarecompiledbytheTechnicalCommitteeTC31.Asacertificationscheme,theIECEx creates a global framework for the independent inspection and certificationofdevicesandservicesrelatingtoexplosionprotection.LikeATEX,IECExdividestheareasatriskintozonesonthebasisofthefrequencyanddurationof the hazard.

11.3.USA–NEC

IntheUS,electricalequipmentthatisusedinpotentiallyexplosiveareasisgovernedbytheNational Electrical Code (NEC).UnliketheregulationsinEuropeandtheIECExscheme,theNEC500–504dividesthepotentiallyexplosiveareasintothreeclasses(ClassesItoIIIforgases,dustsandfibres)andtwodivisionsforthefrequencyanddurationofthepresenceofthesesubstances.In1996,NEC505–506 introduced a zone model similar to the international scheme, parallel to the class model.EquipmentthatistobeusedinminingiscertifiedaccordingtotheregulationsoftheMineSafetyandHealthAdministration(MSHA).

11.4.Canada–CEC

InCanada,approvalisissuedinaccordancewiththeCanadian Electrical Code (CEC 18). Theclassificationoftheareaswaspreviouslybasedonthedivisionmodel,asisthecaseintheUS.SincethelastrevisionoftheCECfrom2015,fornewsystemsandnewdesigns,thezonemodelexclusivelyapplies,similartotheIECEx.Oldequipmentaccordingtothedivisionmodelmaybecontinuedtobeoperatedaccordingtothepreviousregulations(AnnexJ18).TheCanadianprovincesdecideontheimplementationoftheCECseparately,inparts,somesupplements are added.

11.5. Brazil – INMETRO

Brazil’scurrentsetofregulationsistheInmetro Directive 179/2010. This directive accepts certificatesincompliancewiththeIECExschemedirectly,butunlikeIECExcertificatestheyareonlyvalidforthreeyears.OthercertificatessuchasATEXareonlyrecognisediftheyareharmonisedwiththeIECstandards60079.

11.6.EurasianCustomsUnion–TRCU

RussiaformedtheEurasianCustomsUnionEACwithBelarus,Kazakhstan,ArmeniaandKyrgyzstan.Thisresultedinuniformregulationsbeingimplementedinthesecountries.Explosionprotection is regulated in the directive TR-CU 012/2011.EACcertificatescanbeissuedforaone-offdelivery,for1,3orupto5yearsvalidity.ATEXorIECExcertificatesareacceptedasthebasisfortheEACcertification.

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11.7. India – PESO

InIndia,electricalequipmentinpotentiallyexplosiveareasneedstobeapprovedbythePESO–PetroleumandExplosiveSafetyOrganization. In the approval of equipment the Indian regulations differentiate between devices manufactured in India and devices imported to India. ForIndiandevices,thenationalstandardsapplyexclusively,whicharebasedinpartsonoutdatedversionsoftheIECorENstandards.Forimporteddevices,IECExorATEXcertificatesaccordingtothelateststandardsarerequired.ApprovalcanonlybegrantedbytheCCoE – ChiefControllerofExplosivesviaanaccreditedIndiantestlaboratory.Testreportsissuedbynon-Indiantestlabsaretakenintoaccountintheobligatoryinspection.The DirectorGeneralofMiningSafety(DGMS) is responsible for products used in mining.

11.8.China–NEPSI

CertificationinChinaissimilartotheIECExscheme.ItisbasedonIECandENstandardsthathavebeenadopteddirectlyormodified.ATEXorIECExcertificatescanbeusedasabasisfortheChinesecertification.NEPSIcertificatesmustberenewedafterfiveyears.

11.9. Korea – KOSHA

CertificationisalsocarriedoutinaccordancewiththeIECExschemeinKorea.TheKoreanregulationsarealsobasedonIECandENstandardsthathavebeenadoptedwithoutchangeormodified.ATEXorIECExcertificatesthathavealreadybeenissuedcanformthebasisofcertification,althoughadditionalnationalprovisionsmustbetakenintoaccount.

11.10. Japan – TIIS

InJapan,electricalequipmentusedinexplosionprotectionapplicationsmustbecertifiedbytheTIIS–TechnicalInstitutionofIndustrialSafety.ThestandardsforignitionprotectiontypesaremainlybasedonthestandardsseriesIEC60079.However,inparts,olderversionsofthesestandardswereharmonisedandchangesanddeviationswereincluded.TIIScertificatesarevalidfor3yearsandthenneedtoberenewedorextended.Thestandardsonlyapplyfordevicesforareasatriskofgasordust.GroupI(mining)devicesdonotfallundertheTIISscheme,andalsodonotplayagreateconomicrole,asthereisonlyoneremainingcommercialcoalmineinJapan.

11.11. Australia, New Zealand

AustraliaandNewZealandhaveadoptedtheIECExschemeintheirnationalregulations.ThismeansthatIECEx-certifiedproductscanbeuseddirectly.TheonlyexceptionisthestateofQueensland,whichstillhassomeindependentauthorisations.TheSecretariatfortheIECExsystemisbasedinAustralia.


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12. Comparisonofthemainapprovalregulations ATEX – IECEx – NEC

12.1. ATEX

ATEXisaregulationthataimstofacilitatefreetradewithintheEU.Itprescribesessentialsafetyprecautions to protect workers. The ATEX Directive governs both electrical and non-electrical equipment and includes equipment used in mining.Themanufacturerhastoprovideverificationofsafetyandconformitywiththedirective.Thisverificationformsthebasisofauthorisationtolaunchequipmentforpotentiallyexplosiveareasonthemarket.Theconformityprocedurehasdifferentlevelsdependingontheequipment’sgroup/category,withanotifiedbodyneedingtobeinvolvedinsomecases.Anotifiedbodyisaconformityassessmentbody(suchasTÜV-SüdorDEKRA)accreditedbyanEUauthoritythatisauthorisedtoperformconformityassessmentsinaccordancewiththedirectivesasanindependentthirdparty.AlistofthenotifiedbodiesisavailableontheEuropeanCommission’sofficialwebsite(http://ec.europa.eu/growth/tools-databases/nando/index.cfm).AstheCEmarkingistobeissuedinaconformityassessmentbasedontheATEXDirectiveitcansometimesbenecessarytoincludeotherEUdirectives.Itisnotmandatorytoapplytheharmonisedstandards.However,ifthestandardsarefulfilled,thereisapresumptionofconformity–thatis,thesafetyprecautionsareconsidered tobefulfilled.Specificationsordraftstandardscanalsobeusedintheassessment.Thisallowsnewtechnicaldevelopmentstobeaccommodatedimmediately.Thecertificationdocumentsarekeptbythenotifiedbodyorbythemanufacturer.Theyarenotavailable for the user to access.

12.2.IECEx

The IECExEquipmentSchemeisanall-inclusivecertificationprocedure.Itcoversthetypetest,manufacturermonitoring,producttestingduringproduction,inspectionofthequalitysystemandmarketsurveillance.Originallydevelopedmainlyforelectricalequipment,theIECExEquipmentScheme has since been expanded to cover non-electrical equipment.TherelevantIECandISOstandardsneedtobefulfilled.Thecertificatesareissuedbyanindependentthirdparty.InadditiontotheIECExEquipmentSchemeforthecertificationofequipment,thereisalsoacertificationsystemforrepairworkshops(IECExCertifiedServiceFacilityScheme)andanIECExCertificationofPersonalCompetencestocertifytheskillsofexplosionexperts.Thisisintended to ensure that standards remain harmonised in the selection of service providers in equipmentandsystemprojectplanningandintheskillsofworkersinserviceandmaintenance.TheIECExsystemdoesnotcovertheworkplacelayoutandassessmentlikeATEX153does.Thisisstillgovernedbythenationalpublicauthorities.AlldocumentsandissuedcertificatescanbedownloadedfromtheIECExwebsite(www.iecex.com).AlthoughallmajorindustrialstatesactivelyparticipateintheIECandtheIECExsystem,onlyafewcountriesrecognisetheIECExcertificatesdirectly.Inmostcasesitisstillnecessarytoinvolve national bodies.

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12.3.NEC500–504

IntheUS,asystemhasbeendevelopedforexplosionprotectionthatsignificantlydiffersfromtheIECEx/ATEXsystemsthatarecustomaryworldwide.TheUSsystemdividesupthepotentiallyexplosiveareasinadifferentwayandtakesadifferentapproachtothedesignofequipmentandtheinstallationofsystems.UnlikeIECExandATEX,itdividesupflammablesubstancesinthreedifferentclasses:Class Icoversflammablegases,vapoursandmists.TheyaredividedintogroupsAtoDonthebasisoftheirflammability,withthemosthazardoussubstancessuchasacetyleneassignedtoGroup A and substances such as propane gas assigned to Group D. This division is quite differenttothemorecommonwayofdividingthegasgroups,withGroupAcontainingtheleasthazardousgasesandGroupCcontaininghighlyhazardousgasessuchasacetylene.Dusts are assigned to Class II. Like the gases, the dusts are subdivided into groups on the basis ofthematerialtype:Group E contains metal dusts, Group F dusts that contain carbon and Group G organic dusts such as grain dust.There is also a Class IIIthatcontainsflammableorganicfibresandlintssuchascottonandviscose. This class is not subdivided into groups.Likethezonesystem,areasaredividedupinNEC500accordingtothefrequencyanddurationofhazardousconcentrations.Insteadofthreezones,thereareonlytwodivisions:Division 1coversallareaswherehazardousconcentrationscanoccurcontinuouslyoroccasionallyundernormalconditions–i.e.innormaloperationandinregularmaintenanceandrepair work.Division 2 covers all areas where explosive concentrations can be expected in the event of an accidentormalfunction,butarenotlikelyinnormalconditions.ThedivisionsforfibresandlintsinClass IIIareslightlydifferentfromthoseforgasesanddusts.Division 1 covers all areas where the materials are worked with or transported between one processing step and the next, while Division 2coversallareaswherehighlyflammablefibresandlintsarestoredortransportedseparatelyfromprocessing.ThemaximumsurfacetemperaturesarecategorisedinthesamewayasintheATEX/IECExsystem,intemperature classes ranging from T1 to T6. Temperature classes T2, T3 and T4 have additional subclasses. Dusts are divided up in the same temperature classes as gases. UnlikeATEX,NEC500doesnotspecifythepermissibletemperaturesdirectly.Example of the categorisation of electrical equipment for areas at risk of gas explosion in the divisionmodel:

Class I Division 1 Group A T4

Hazard class Class IAreaclassificationDivision 1GasgroupATemperature class T4


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12.4.NEC505–506

NEC505and506aremorestronglyalignedtotheexistinginternationalIECEx/ATEXsystemsthanNEC500etseq.Theareasaredividedupintothreezones,asinIECEx/ATEX,ratherthanindivisions.ThegroupsandignitionprotectiontypesarealsodividedupinasimilarwaytoIECEx/ATEX.ThetemperatureclassesrangefromT1toT6,astheyareinIECEx/ATEX,withnoadditional subclasses.Example of the categorisation of electrical equipment for areas at risk of gas explosion in the zonemodel:

Class I Zone 1 AEx ia IIC T4

Hazard class Class IAreaclassificationZone 1Electrical equipment American Standard AExIgnitionprotectiontypei protection level aGroupII CTemperature class T4

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13. Bibliography

Directive 2014/34/EU

Directive2014/34/EUoftheEuropeanParliamentandoftheCouncilof26February2014ontheharmonisationofthelawsoftheMemberStatesrelatingtoequipmentandprotectivesystemsintendedforuseinpotentiallyexplosiveatmospheres(recast) OfficialJournaloftheEuropeanUnion

Directive 1999/92/EC

Directive1999/92/ECoftheEuropeanParliamentandoftheCouncilof16December1999onminimumrequirementsforimprovingthesafetyandhealthprotectionofworkerspotentiallyatriskfromexplosiveatmospheres OfficialJournaloftheEuropeanUnion

ATEXGuidelines GuidelinefortheimplementationofDirective2014/34/EUoftheEuropeanParliamentandtheCouncilof26February2014ontheharmonisationofthe laws of the Member States relating to equipment and protective systemsintendedforuseinpotentiallyexplosiveatmospheres 1. Edition April 2016 EuropeanCommission

EN 1127-1 Explosive atmospheres – Explosion prevention and protection – Part1:Basicconceptsandmethodology Beuth-Verlag,Berlin

EN 13463 Seriesofstandards:Non-electricalequipmentforuseinpotentially explosive atmospheres Beuth-Verlag,Berlin

EN 60079 Seriesofstandards:Explosiveatmospheres Beuth-Verlag,Berlin

EN 80079 Seriesofstandards:Non-electricalequipmentforexplosiveatmospheres Beuth-Verlag,Berlin

Publication GrundlagenExplosionsschutz[Basicsofexplosionprotection] R. Stahl, Waldenburg

Publication GrundlagenExplosionsschutz[Basicsofexplosionprotection] Crouse-Hinds,Eberbach

Publication 2014CodeDigest Crouse-Hinds,Syracruse

Publication GrundlagenExplosionsschutz[Basicsofexplosionprotection] Bartec, Bad Mergentheim


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