Hazardous Areas - Protection Techniques according European IECEx

Electronic or electrical equipment of any type for use in European hazardous areas must be ATEX certified as required by the EU directive 94/9/EC - also known as the ATEX directive.

Basis for equipment certification is the hazardous area classification system used, the

• Zone system in Europe and most of the world
• Class/Division system and Zone system in North America

Ex marking

The ATEX directive classifies equipment into groups and categories which are defined by the marking on the equipment. A typical marking can be 

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Ex Classification - Equipment Marking

	0158		II	2G	EExd	IIB	T4
EU Directive	Notified Body Code	Explosion Proof	Equipment Group	Category Gas/Dust	Type of Certificate Type of Protection	Group Sub Group	Temperature Classification

The different parts of the nomenclature are explained below:

CE Mark

Informs that the product complies with the European Directive.

Notified Body Code

Informs witch official Notified Body did the testing and certification of the product.

Explosion Proof

The explosion proof Ex tag is required for certified equipment in accordance with the ATEX directive.

Equipment Group

The tag for equipment group relates to groups in the Zone system where

• I - is for use in underground mines
• II - is for all other places

Category - Gas/Dust

Category

The tag for category relates to the Zone in the Zone system where

• 1 - is for equipment for use in areas where an explosive atmosphere is present continuously or for long periods or frequently
• 2 - is for equipment for use in areas where an explosive atmosphere is likely to occur in normal operations
• 3 - is for equipment for use in areas where an explosive atmosphere is unlikely to occur in normal operations

Gas/Dust

• G - equipment certified for flammable gases
• D - equipment certified for dust atmosphere

Type of Certificate - Type of Protection

Type of Certificate

Types of certificate indicates standards used for the certification.

• EEx - European standards
• AEx - American standards

Type of Protection

Types of protection indicates the level of protection concepts the equipment is designed for. The protection concepts are divided in to sub classes.

Encapsulated

Protection applied by encasing the components in a resin type material.

The protection is referred to as "Ex m".

Sub divisions ma for Zone 0 and mb for Zone 1.

Flameproof

The enclosure can withstand the pressure developed during an internal explosion of an explosive mixture. The explosion is not transmitted to the explosive surrounding atmosphere and the enclosure operates with a temperature to low for the surrounding explosive gas or vapor to ignite.

This protection is referred to as "Ex d".

Intrinsically Safe

Electrical equipment is under normal or abnormal conditions incapable of releasing sufficient electrical or thermal energy to cause a ignition of the hazardous surrounding atmospheric mixture.

This protection is referred to as "Ex i".

Sub divisions ia  for Zone 0, ib for Zone 1 and ic for Zone 2.

Increased Safety

High quality and very robust components. Various measures are applied to reduce the probability of excessive temperatures and the occurrence of arcs or sparks in the interior and on the external parts of the equipment. Increased safety may be used with flame-proof type of protection.

The protection is referred to as "Ex e".

Oil Filled

Protection applied by submerging the components in oil.

The protection is referred to as "Ex o".

Pressurized/purged

Protection applied by keeping a positive pressure in the enclosure relative to the surrounding atmosphere with air or an inert gas. With an overpressure monitored, maintained and controlled - the surrounding ignitable atmosphere can not come in contact with energized parts of the apparatus.

The protection is referred to as "Ex p".

Sub divisions px or py for Zone 1 and pz for Zone 2.

Sand/Powder/Quartz Filled

Protection applied by covering the components with sand, powder or quartz.

The protection is referred to as "Ex q".

Non Incendive

A protection applied to electrical equipment in such a way that normal operation is not capable of igniting surrounding explosive atmospheres.

The protection is referred to as "Ex n".

Special Protection

Any method which can be shown to have the required degree of safety.

The protection is referred to as "Ex s".

• Protection Techniques for Hazardous Areas - North America

Group - Sub Group

The tag for equipment group relates to groups in the Zone system where

• IIA - Atmosphere containing propane, acetone, benzene, butane, methane, petrol, hexane, paint solvents or gases and vapors of equivalent hazard.
• IIB - Atmosphere containing ethylene, propylene oxide, ethylene oxide, butadiene, cyclopropane, ethyl ether, or gases and vapors of equivalent hazard.
• IIC - Atmosphere containing acetylene, hydrogen, carbon disulphide or gases and vapors of equivalent hazard.
• IIIA - Atmosphere containing combustible flyings.
• IIIB - Atmosphere containing non-conductive dust.
• IIIC - Atmosphere containing conductive dust.

Temperature Classification

Hazardous area equipment is classified according to maximum surface temperature produced under fault conditions at ambient temperature 40 ^oC (104 ^oF), or as otherwise specified.

Temperature ^oC
K
^oF

Length m
km
in
ft
yards
miles
naut miles

Area m²
km²
in²
ft²
miles²
acres

Volume m³
liters
in³
ft³
us gal

Weight kg_f
N
lbf

Velocity m/s
km/h
ft/min
ft/s
mph
knots

Pressure Pa
bar
mm H₂O
kg/cm²
psi
inches H₂O

Flow m³/s
m³/h
US gpm
cfm