ATEX Zones: Definitions, Zoning, Solutions
Each year, 150 work-related work accidents are recorded in France, on average. More than 15% of them generate significant human and material damage. On construction sites or in the industrial environment, the risk of explosion is all the more important in the presence of flammable substances (gas, steam, dust ...). To avoid any danger, it is essential to define the ATEX areas of a workplace and to engage all the securing procedures of the perimeters concerned.
What is a ATEX zone?
On industrial sites and construction sites, staff safety and equipment is a priority. Accurate devices are put in place to prevent possible dangers. Among them, the ATEX indication.
ATEX is the abbreviation of the expression "Explosive atmosphere". A ATEX is an environment in which the risk of explosion is high due to the presence of fuels, visible or not with the naked eye. According to EN 1127-1, an explosion is "a brutal reaction of oxidation or decomposition involving elevation of temperature or pressure or both simultaneously". The propagation of combustion is almost immediate, accompanied by flames and heat waves. A ATEX can form in Normal operating conditions or accidentally by the flight of one or more fuels.
In an ATEX, the air mixes with flammable materials. The explosion occurs when six simultaneous conditions are met:
- the presence of a combustion (usually the oxygen of the air)
- The presence of a fuel (propane, hydrogen, coal, wheat flour ...)
- The presence of a source of inflammation (spark, static electricity, heat ...)
- The particular state of fuel (gas, dust, fog ...)
- Obtaining an explosive domain: the mixture is neither too poor nor too rich in fuel
- A confined space
Attention : Industrial sites are not the only places where ATEX are formed. Any activity or installation involving the handling and handling of flammable substances can also run this risk.
Important definitions about hazardous areas
Each ATEX zone is normalized according to its degree of danger. In accordance with ATEX 99/92 / EC, the employer is required to assess the risk of explosion on their site and to make a rating classification.
One Zoning ATEX Must be made by a competent speaker, so that the workplace is defined and subsequently secure. The identification of ATEX zones goes through an audit of the entire production tool.
Article 7 of the ATEX Directive 1999/92 / EC thus specifies this obligation: "The employer subdivided into zones the locations where explosive atmospheres may arise, in accordance with Annex I."
How to delimit the ATEX zones?
Zoning is to define parts of a site on which explosion risk can be formed. These locations are qualified as dangerous and delimited areas according to their degree of dangerousness.
The delimitation of an ATEX zone is an important step for the safety of workers working in areas where explosive atmospheres can form. The ATEX zones are defined by the European Directive 1999/92 / EC and are used to classify work areas based on their level of explosion risk.
The delimitation of an ATEX zone is based on a risk assessment that determines the probability that an explosive atmosphere is formed in a given area. This assessment takes into account several factors, such as the frequency and duration of the presence of explosive substances, ventilation and potential sources of ignition.
- Once the risk areas have been identified, they must be clearly delineated. The delimitation methods may vary depending on the circumstances, but here are some current options: ground marking: the areas can be delimited by ground markings of different colors for each zone, which makes it possible to better identify the limits.
- SIGNALING: Panels and labels can be used to indicate the presence of ATEX zones and provide information on specific risks.
- Physical barriers: Physical barriers can be used to separate areas at risk areas where the risk of explosion are lower.
- Use of specific equipment: Equipment such as luminaires, fans and engines can be designed for use specifically in ATEX areas. It is important to note that the delimitation of the ATEX zones must be regularly re-evaluated and updated according to changes in working conditions.
Regulation
An area is called ATEX when it is used to store or handle flammable materials. The degree of dangerousness of an ATEX zone is evaluated according to the quantity and nature of the latter. The higher the level, the greater the risks and the more regulations are strict.
- Directive 2014/34 / EU (ATEX 95), relating to equipment used in ATEX zone;
- and Directive 1999/92 / EC (ATEX 137), relating to the safety of workers in an ATEX zone.
These guidelines require employers to master the risk of explosion on their site, as well as other occupational risks. The goal is to ensure safety and improve the health of people who may be exposed to ATEX's risks.
- Evaluate the risk of explosion on its site
- Identify, classify and delimit the ATEX zones
- Establish technical and organizational protection measures (prevention, training, maintenance ...)
- Provide devices and equipment specific to hazardous areas
- draft a Drcpe (Document on protection against explosions)
Since the entry into force of Directive 1999/92 / EC in July 2003, the explosion risk assessment is mandatory. The workplace as well as equipment must be brought into conformity, under penalty of a fine of up to 10,000 euros (Article L. 4741-1 of the Labor Code).
The ATEX zoning takes over the following steps:
- Collection of chemical physico data from combustible products on the site
- Functional analysis of facilities implementing flammable products
- Determination of the sources of release and the likelihood of appearance of an ATEX (explosive atmosphere)
- Characterization of the zone (dangerous and extended)
- Study of sources of inflammation
Classification of areas
There are three types of areas defined by the IEC (1986), by the Ministry of Labor (1988) and by the Ministry of Industry (1991).
This classification is refined in the ATEX directive, which no longer speaks of the areas but of apparatus categories, depending on the likelihood of the formation of an explosive mixture, and two different applications depending on the nature of the mixture (gas or dust).
- Permanent risk: The explosive mixture is permanently present
- Frequent risk: An explosive mixture of gas or vapors is likely to form in normal installation of the installation
- Occasional risk: An explosive mixture can only appear in case of abnormal operation of the installation
| Areas | Material category | |
|---|---|---|
| Gas | 0: Permanent presence 1: occasional presence 2: Rare presence | -> 1g -> 2g or 1g -> 3G, 2G or 1G |
| Dust | 20: Permanent presence 21: occasional presence 22: Rare presence | -> 1g -> 2g or 1g -> 3G, 2G or 1G |
These risks have created 3 categories that determine the level of protection of devices
- Category 1: Very high level of protection: the explosive mixture is constantly present, or for a long period, or frequently
- Category 2: High level of protection: an explosive mix will probably be manifested
- Category 3: Normal level of protection: An explosive mixture has a low probability of manifesting, and will only remain for a short period.
| Device category | Flammable substance | Degree of protection | Protection, default values | |
|---|---|---|---|---|
| APPARATUS GROUP I (MINES) | M1 | Methane dust | Very high level | 2 protection channels or default values |
| M2 | Methane dust | High level | 1 lanes of protection Standard operation | |
| APPARATUS GROUP II (MINES) | 1 | Gas, vapors, mists, dusty | Very high level | 2 protection channels or default values |
| 2 | Gas, vapors, mists, dusty | High level | 1 Path of protection Current and frequent disruption | |
| 3 | Gas, vapors, mists, dusty | Standard | Level of protection required |