Electrical ATEX and IECEx Equipment

Electrical equipment intended for use in potentially explosive atmospheres must be designed to prevent potential ignition sources from igniting the surrounding explosive atmosphere.

Various types of protection are used for this purpose, depending on the equipment, the intended environment and the required Equipment Protection Level (EPL).

The requirements are specified in the EN IEC 60079 series of standards, with EN IEC 60079-0 providing the general requirements for construction, testing and marking.

Below is an overview of the main electrical types of protection used in explosive gas and dust atmospheres.

Common Electrical Types of Protection

Ex d – Flameproof Enclosure (IEC 60079-1)

With type of protection Ex d, an explosive gas atmosphere may enter the enclosure. The enclosure is designed to withstand an internal explosion without allowing the explosion to propagate to the surrounding atmosphere.

Flames and hot combustion gases are sufficiently cooled as they pass through specially designed flamepaths.

Ex d is commonly used for enclosures containing switching equipment, electric motors and other equipment that may produce sparks or arcs during normal operation.

Ex e – Increased Safety (IEC 60079-7)

With Ex e, additional constructional measures are applied to prevent effective ignition sources, such as excessive temperatures, sparks and electrical arcs.

This type of protection includes two protection levels:

Ex eb: suitable for EPL Gb, generally used in Zone 1.
Ex ec: suitable for EPL Gc, generally used in Zone 2.

Ex e is commonly applied to connection boxes, terminal enclosures, electric motors and lighting equipment.

Ex i – Intrinsic Safety (IEC 60079-11)

Intrinsic safety limits the electrical and thermal energy in a circuit to a level that cannot ignite an explosive atmosphere.

The assessment considers parameters such as voltage, current, power, capacitance and inductance.

Three protection levels are distinguished:

Ex ia: EPL Ga, suitable for Zone 0.
Ex ib: EPL Gb, suitable for Zone 1.
Ex ic: EPL Gc, suitable for Zone 2.

Ex i is widely used in instrumentation and control equipment, sensors, process transmitters and control systems. The assessment covers not only the equipment itself but also the associated intrinsically safe circuits.

Ex p – Pressurization (IEC 60079-2)

With Ex p, an enclosure is maintained at a positive pressure using a suitable protective gas, such as clean instrument air or an inert gas. This prevents an explosive atmosphere from entering the enclosure.

Depending on the required protection level, Ex pxb, Ex pyb and Ex pzc may be applied.

This type of protection specifies requirements for pressure monitoring, purging where applicable, and protective functions.

Ex p is commonly used for control panels, analytical equipment and other systems containing components that are not individually explosion-protected.

Ex m – Encapsulation (IEC 60079-18)

With Ex m, electrical components are completely or partially encapsulated in a suitable compound to prevent potential ignition sources from becoming effective.

The encapsulating compound must meet specific electrical, thermal, mechanical and chemical requirements.

Depending on the required protection level, Ex ma, Ex mb and Ex mc are distinguished.

This type of protection is commonly used for electronic circuits, sensors, coils and smaller electrical components.

Ex t – Protection by Enclosure for Dust Atmospheres (IEC 60079-31)

With Ex t, the enclosure prevents combustible dust from entering in hazardous quantities and ensures that the surface temperature does not present an ignition hazard.

Protection is based on factors including the degree of protection (IP rating), enclosure construction and limitation of the maximum surface temperature.

Depending on the required protection level, Ex ta, Ex tb and Ex tc are distinguished.

Ex t is widely applied to electrical equipment used in explosive dust atmospheres, including motors, control panels, sensors and lighting equipment.

Other Electrical Types of Protection

In addition to the types of protection described above, several other methods are available:

Ex o – Liquid Immersion (IEC 60079-6): potential ignition sources are protected by immersion in a suitable protective liquid.
Ex q – Powder Filling (IEC 60079-5): electrical components are surrounded by a fine-grained filling material that prevents internal ignition sources from igniting an explosive atmosphere.
Ex n – Type of Protection 'n' (IEC 60079-15): includes enclosed-break devices (Ex nC) and restricted-breathing enclosures (Ex nR) for Zone 2 applications. The former Ex nA and Ex nL types of protection have been replaced by Ex ec and Ex ic, respectively.
Ex op – Protection by Optical Radiation (IEC 60079-28): protective measures to prevent optical radiation, for example from lasers or fibre-optic systems, from igniting an explosive atmosphere.

Selecting the Appropriate Type of Protection

The selection of a suitable type of protection depends on several factors, including:

The intended explosive gas or dust atmosphere.
The required ATEX equipment category and Equipment Protection Level (EPL).
The gas or dust group and temperature classification.
The electrical and thermal characteristics of the equipment.
The operating conditions and possible fault conditions.

In many applications, different types of protection are combined to achieve a practical and safe design.

Further information about equipment identification can be found on our page about ATEX marking.

Design, Assessment and Certification

When developing electrical Ex equipment, the selected type of protection is only one aspect of the assessment. General construction requirements, material suitability, electrostatic hazards and maximum operating temperatures must also be considered.

For example, temperature measurements may be necessary to determine both the maximum surface temperature and the service temperature of individual components.

MIBEX supports manufacturers and machine builders with explosion-safe design, selection of suitable types of protection, technical assessments and preparation of documentation for ATEX and IECEx certification.

Do you have questions about electrical types of protection or the assessment of your Ex equipment? Please feel free to contact us to discuss your requirements.