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ATEX

Equipment Categories Associated with the ATEX Directive

This explanatory page is focusing on the gas side of the ATEX (Explosive Atmospheres) directive as being more relevant to the products which we sell

EQUIPMENT GROUPS

The ATEX directive identifies two GROUPS of equipment

GROUP 1 equipment is intended for use in mining, or underground applications. Divided into categories M1 and M2. M1 identifies equipment that must continue to operate when a potentially explosive atmosphere is present. M2 identifies equipment that does not operate when a potentially explosive atmosphere is present

GROUP 2 equipment is intended for all other above-ground applications. Divided into CATEGORIES 1,2 and 3

EQUIPMENT CATEGORIES

CATEGORY 1 equipment is intended for use in ZONE 0 situations
CATEGORY 2 equipment is intended for use in ZONE 1 situations
CATEGORY 3 equipment is intended for use in ZONE 2 situations

ZONED areas are areas where there is a risk of flammable material being released to atmosphere

ZONES FOR GASES

ZONE 0 is the highest risk zone where an explosive atmosphere is expected to exist continuously or for very long periods of time
ZONE 1 is an area where an explosive atmosphere is expected to exist for short periods of time, but during a year the accumulation of such events is not in excess of 1000 hours
ZONE 2 is an area where an explosive concentration of flammable material is not expected and should it be released it will only exist for a very short period of time and where the accumulation of events over a year does not exceed much in excess of 10 hours

It is mandatory for manufacturers to obtain an EC Type Examination Certificate from a notified body if they are manufacturing electrical equipment in Categories M1, M2, 1 and 2 or diesel engine protection systems in Category 2. In all other cases manufacturers are free to certify their own equipment

EXPLOSIVE ATMOSPHERE

Gas G
Dust D

EUROPEAN STANDARD - Identified as letter 'E' in the Designation

EXPLOSION PROOFNESS - Identified as letters 'Ex' in the Designation, usually found following the above 'E' and thus marked as 'EEx'

RANGE OF APPLICATION

Fiery Mine Areas I
Other Hazardous Areas II

EXPLOSION GROUPING OF GASES

Gases and dusts are classified according to their ignition properties. For Gases and Vapors the EXPLOSION GROUP, (Under Range II above) is called the GAS GROUP, and is determined according to;

  • MESG - Maximum experimental safe gap (IEC 60 079-1A)
  • MIC - Minimum ignition current ratio relative to methane (IEC 60 079-3)
GAS GROUP MESG MIC
IIA >0.9 mm >0.8
IIB 0.5 - 0.9 mm 0.45 - 0.8
IIC <0.5 mm <0.45

The danger levels of gases increases from GAS GROUP IIA to IIC

TEMPERATURE CLASSING

Temperature classing is based upon the auto-ignition temperature of a given substance, it is not relevant to flash points as many people think. The temperature class increases as the auto-ignition temperature decreases, from TEMPERATURE CLASS T1 to T6, therefore Temperature Class T6 offers the highest level of protection

Temperature Class IEC/EN & NEC 505-10 Max. Sfc. Temp. of Equipment (Celcius) Auto Ignition Temperature of Substance
T1 450 >450
T2 300 >300 to <450
T3 200 >200 to <300
T4 135 >135 to <200
T5 100 >100 to <135
T6 85 >85 to <100

EXAMPLES OF SUBSTANCE GROUPING

GAS GROUP T1 T2 T3 T4 T5 T6
I Methane          
IIA Acetone Ethanol Diesel Fuel Acetyldehyde    
  Ethane Cyclohexane Aircraft Fuel      
  Petroleum Butane Fuel Oil 1,2 & 3      
  Propane N-Butyl Alcohol Kerosene      
  Methanol Propan-2-ol Gasoline      
  Toluene Cumene Turpentine      
  Benzene   N-Hexane      
  Acetic Acid   Heptane      
  Xylene          
  Ammonia          
IIB Coal Gas (Town Gas) Ethylene Ethylene Glycol Ethyl Methyl Ether    
    Ethylene Oxide Hydrogen Sulphide      
    Propan-1-ol Tetrahydrofuran      
IIC Hydrogen Acetylene       Carbon Disulphide

STANDARDS FOR METHODS OF PROTECTION

The method of protection refers to the standard to which the device has been produced to. There are ELECTRICAL PROTECTION CONCEPTS, and MECHANICAL PROTECTION CONCEPTS

PROTECTION CONCEPTS

Protection Concept Permitted Zone of Use in The UK Code Letter IEC, EX, CENELEC, EEX Standard IEC/EN
General Requirement - -

60079-0 (Electrical)

13463-1 (Mechanical)

Control of Ignition Sources 1 b 13463-6
Constructional Safety 1 c 13463-5
Flameproof Enclosure

1, 2

1

d

60079-1 (Electrical)

13463-3 (Mechanical)

Increased Safety 1, 2 e 60079-7 (Electrical)
Flow Restriction 2 fr 13463-2 (Mechanical)
Intrinsic Safety 0, 1, 2 ia 60079-11 (Electrical)
Intrinsic Safety 1, 2 ib 60079-11 (Electrical)
Liquid Immersion 1 k 13463-8 (Mechanical)
Encapsulation 1, 2 m 60079-18 (Electrical)
Encapsulation 0 ma 60079-18
Encapsulation 1 mb 60079-18
Non Incendive 2 n (used locally in the UK) 60079-15 (Electrical)
Energy Limited 2 nL 60079-15 (Electrical)
Non Sparking 2 nA 60079-15 (Electrical)
Restricted Breathing 2 nR 60079-15 (Electrical)
Enclosed Break 2 nC 60079-15 (Electrical)
Pressurisation

1, 2

1

2

p

p

np

60079-2 (Electrical)

13463-7 (Mechanical)

60079-15 (Electrical)

Oil Immersion 2 o 60079-6 (Electrical)
Powder Filling 2 q 60079-5 (Electrical)
Special 1, 2 s  

INGRESS PROTECTION

Hazardous area equipment typically requires a minimum IP rating of IP54, but may be assessed and tested to higher ratings as detailed in the charts below. For full definition of IP Ratings, see IEC/EN 60529

DUST  
IP5x Dust Protected
IP6x Dust Tight

 

WATER  
IPx4 Splashing Water
IPx5 Water Jets
IPx6 Powered Water Jets
IPx7 Temporary Immersion
IPx8 Continuous Immersion

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