HAZARDOUS AREA classification Zone wiseZone ClassificationDefinitionThe classification of a Zone is a complex problem with the main factors to consider: The probability of the presence of Gas or Vapour or Dust The quantity and duration of hazardous environment The amount of ventilation The nature of Gas being lighter or heavier than AirThe division of the plants or parts into Zones is generally undertaken by the supervisory authority in that industry with process engineers / chemists at the design and / or construction stage.Zone 0Continuously Hazardous ( Protection Technique Allowed)Ex ia Intrinsically SafeEx ma Encapsulation

Zone 1Frequently Hazardous (Protection Technique Allowed)Ex ib Intrinsic SafetyEx d FlameproofEx e Increased SafetyEx p Pressurized or PurgedEx s Special Protection

Zone 2Infrequently Hazardous (Protection Technique Allowed)Ex nNon-sparking

Typical Example of Zone

HAZARDOUS AREA EQUIPMENTClassification of Hazardous AreasDefinition Explosive gas vapours atmospheres Combustible Dust Specific occupanciesGroup ClassificationHazardous area equipment is specified in terms of the types of gases present or where dust is present. Group I Underground mining applications Group II Industries other than mining Group III Industries having dust or fibresGroup I :Equipment has a representative gas of Methane and all equipment used in underground mining applications fall into this category.Group II:As shown in the below table this Group II is segmented into three different representative gas groups, IIA, IIB and IIC.Group III:Equipment is segmented concerning the thickness of the dust Practice A and B regarding maximum surface temperatures relatingto the ignition temperatures of the material. The Group III dusts are segmented into three different representative dusts IIIA, IIIB andIIIC, with the worst case being IIIC for conductive dusts.Group Classification and Representative Gas Data Table

Group ClassificationRepresentative Gas

IMethane

IIAPropane

IIBEthylene

IICHydrogen, Acetylene

Equipment Protection Levels EPLsThe introduction of Equipment Protection Levels ( EPLs ) is provided to give further segregation of products and protection techniquesfor hazardous areas. The EPLs consider assessment of the risk involved with an installation and the suitable equipment protectiontechniques. These EPLs are generally in line with Zones, however on risk assessment a higher EPL may be used to provide higherprotection. Where an EPL is specified on a hazardous document it takes precedence over the Zone classification.Group Classification and Zone Data Table

Group IGroup IIGroup III

Zone 0 EPL MaZone 0 EPL GaZone 20 EPL Da

Zone 1 EPL Ma and MbZone 1 EPL Ga, GbZone 21 EPL Da, Db

Zone 2 EPL Ga, Gb and GcZone 22 EPL Da, Db and Dc

HAZARDOUS AREA EQUIPMENTZone Protection TechniquesDefinitionThe protection technique is a specific process with negates one of the three components of combustion.The Australian standards are based on the International Electrotechnical Commission IEC standards and with the CENELEC standards beings similar and now being harmonised with IEC, in respect of Zone classification, Gas groups temperature ratings and testing methods.Types of Application and Protection Techniques Data TableZone Protection Techniques Data Table

HAZARDOUS AREAS AND HAZARDOUS AREA EQUIPMENTExplosion Protection TechniquesTypes of Protection Techniques DataTable

MethodSymbolType of Protection

ExclusionEx tDDust-excluding ignition proof

Ex mEncapsulation

Ex nNon-sparking (hermetically sealed devices, sealed devices and restricted breathing)

Ex pPressurized enclosure/Rooms

Ex qSand-filled (powder filling)

Explosion containmentEx dFlameproof enclosure

Energy LimitationEx iIntrinsic safety

DilutionEx vVentilation

Avoidance of ignitionEx eIncreased safety

Ex nNon-sparking (inherently non-sparking)

Types of Application and Protection Techniques Data Table

Hazardous areas are defined by three main criteria: The type of hazard The likelihood of the hazard being present in flammable concentrations The (auto) ignition temperature of the hazardous material

The type of hazard (Groups)The hazard will be in the form of a gas, vapour, dust or fibre.

Gases and VapoursGases and vapours are categorized in terms of their ignition energy or the maximum experimental safe gap (in respect of flameproof protection). This categorization leads to the Gas Groups:

MiningSurface Industry

Group IGroup II

MethaneIIAIIBIIC

PropaneEthyleneHydrogen

(The gases noted in the table are typical gases for each group.)Group IIC is the most severe group. Hazards in this group can be ignited very easily indeed.Equipment marked as suitable for Group IIC is also suitable for IIB and IIA.Equipment marked as suitable for IIB is also suitable for IIA but NOT for IIC.If equipment is marked, for example, Ex e II T4 then it is suitable for all subgroups IIA, IIB and IIC.