What is IEC 60079-0? General Requirements for Explosive Atmosphere Appliances.
Short answer: IEC 60079-0 is the standard that all electrical and non-electrical equipment used in explosive atmospheres must comply with. general (basic) conditions It is the main standard that defines equipment groups, gas/dust groups, temperature classes, protection levels (EPL), and Ex marking; all other 60079 sub-standards are built upon this foundation.
In the world of explosive atmosphere equipment, everything begins with IEC 60079-0. This standard sets out the common rules that equipment must meet to be classified as 'Ex'; special protection methods such as flameproofing (Ex d), enhanced safety (Ex e), or intrinsic safety (Ex i) are added on top of this foundation. Therefore, understanding 60079-0 is a prerequisite for correctly reading an 'Ex' label and selecting the right equipment.
Equipment Groups
The standard categorizes equipment into three main groups based on the environment in which it will be used:
| Group | Usage environment |
|---|---|
| Group I | Underground mines (fired gas/methane) |
| Group II | Surface facilities containing gas and steam (refinery, chemical, LPG) |
| Group III | Environments containing flammable dust (food, pharmaceuticals, wood) |
Gas Groups and Explosion Intensity
Group II equipment is further subdivided according to the ease of ignition of the gas in the environment: IIA (propane typical), IIB (ethylene) and IIC (Hydrogen, acetylene — the most dangerous). Equipment certified for IIC also covers the lower groups, but not vice versa. Similarly, dust environments are classified as IIIA (flying fiber), IIIB (non-conductive dust), and IIIC (conductive dust).
Temperature Classes (T1–T6)
The surface temperature of Ex equipment is the ignition temperature of the gas in the environment. under It must remain. The temperature class indicates this maximum surface temperature:
| Class | Maximum surface temperature |
|---|---|
| T1 | 450 °C |
| T2 | 300 °C |
| T3 | 200 °C |
| T4 | 135 °C |
| T5 | 100 °C |
| T6 | 85 °C |
For example, in an environment with an ignition temperature of 135 °C, at least T4 (or safer T5/T6) class equipment is required; T1-T3 equipment is insufficient.
Level of Protection (EPL) and Ex Marking
In the modern approach, each piece of equipment has a Equipment Protection Level (EPL) assigned: For gas Ga/Gb/Gc, for dust Da/Db/Dc (a highest level of protection). This directly determines which zone the equipment can be used in. For example, on an Ex label you will see 'Ex db IIC T4 Gb', which means flameproof (d), IIC gas group, T4 temperature class and Gb protection level. During AES inspection, the compliance of each piece of equipment's marking with the requirements of the zone in which it is installed is verified.
Frequently Asked Questions
Is IEC 60079-0 sufficient on its own?
No. 60079-0 provides the basic requirements; the equipment must also comply with the standard for the type of protection to which it is applied (e.g., 60079-1 flameproof, 60079-7 enhanced safety).
Can I use IIC certified equipment in an IIA environment?
Yes. Approved equipment for the most demanding group, IIC, also covers less hazardous IIB and IIA environments; however, the reverse is not possible.
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Related service: Explosive Atmosphere (ATEX/Ex-Proof) Inspections.