In this article, we will see what the ATEX Directive 94/9/EC is, its development over time, the definitions, and some of the ATEX zones concerned.
First of all, the acronym comes from French ATmosphère EXplosive or rather an explosive atmosphere.
This directive, issued by the European Union, defines the safety standards necessary for all equipment and protection systems intended for environments with potentially explosive atmospheres.
In Italy it has come into effect on July 1st, 2003, and serves to guarantee the free movement of goods between the countries of the European Community, outlining fundamental requirements for health and safety.
This directive was repealed in April 2016 through Legislative Decree no. 85 of May 19th, 2016. The new directive, ATEX 2014/34/EU, was published at the end of April 2014 and has come into effect with the decree.
Again, the new directive is aimed at facilitating the circulation of products, so as to protect companies and standardize regulations in all EU countries.
We will better understand the details of this important directive, thanks to the contribution of experts from Sorgato.com
It is important to understand the definitions to identify what exactly are the affected categories of machinery (and devices).
Among the changes to the new direct,ive we also find some definitions.
Let’s see which ones:
- The term “equipment” means all devices, detection and prevention systems, machines and equipment, instrumentation and control devices, intended for business processes, which are likely to cause an explosion.
- ‘Protective systems’ means devices designed to suppress explosions as quickly as possible and to limit the affected area.
- “Manufacturer” means “a natural or legal person who manufactures a product or has it designed or manufactured and markets it under his name or trademark or uses it for his own purposes”.
Among its obligations include: the execution of the conformity procedure, the guarantee that the products are manufactured in compliance with the essential health and safety requirements, the affixing of the explosion protection mark together with a type / series / batch number to allow identification, the preparation of technical documentation.
- An ‘authorised representative’ is ‘a natural or legal person established in the Union who has received a written mandate from a manufacturer authorising him to act on his behalf in relation to certain tasks’. Among its obligations are: relations with the authorities and the provision of the EU declaration of conformity and technical documentation;
- The “distributor” is a natural or legal person, different from the previous two, who makes a product available on the market. Some of its obligations are: to verify the presence of the CE marking on products and documents, and to certify that the storage and transport conditions do not compromise their conformity.
- Finally, the “importer” or rather “a natural or legal person established in the Union who markets on the EU market a product originating in a third country”. Its duties include: preparing the technical documentation and placing compliant products on the market by verifying that the manufacturer has carried out the correct procedure.
Another difference compared to the previous legislation is the extension of the definitions with the additions of the New Legislative Framework (Goods Package 2008) which introduces further innovations with respect to the free movement of products in the EU.
This enlargement in turn consists of two regulations:
- Regulation (EC) 764/2008: laying down procedures relating to the application of certain national technical rules to products lawfully marketed in another Member State;
- Regulation (EC) 765/2008: setting out the requirements for accreditation and market surveillance relating to the marketing of products;
Atex Zones
All environments with potentially explosive atmospheres are classified in this way.
The essential characteristics to fall into the category are related to the phenomenon of combustion, and are:
- Fuel Source
- Oxidizing Agent
- Ignition Source
How are Atex Zones Classified?
They are classified according to the frequency of explosive atmospheres and their duration, whether they are due to gas or dust.
We have zones 0, 1, and 2 if the explosions are due to gas, and 20, 21, and 22 if they are due to dust.
The former is defined as follows:
- Zone 0: Area where an explosive atmosphere consisting of a mixture of air and flammable substances in the form of gas, vapor, or mist is present permanently or for long periods or frequently.
- Zone 1: Area where the formation of an explosive atmosphere, consisting of a mixture of air and flammable substances in the form of gas, vapor, or mist, is likely to occur occasionally during normal activities.
- Zone 2: Area where during normal activities the formation of an explosive atmosphere consisting of a mixture of air and flammable substances in the form of gas, vapor, or mist is not likely to occur or if it occurs, is only of short duration.
The second group, on the other hand, looks like this:
- Zone 20: an area where an explosive atmosphere in the form of a cloud of combustible dust is present permanently or for long periods;
- Zone 21: the area where the formation of an explosive atmosphere is occasionally likely;
- Zone 22: the area where the formation of an explosive atmosphere is not likely and if it occurs, would be short-lived;
Zones 20 and 21 are the most exposed to the risk of explosion, so it is always recommended to place the systems in zone 22. In this case, only one security system is needed and the system can be self-certified.
When it is not possible, the systems must be equipped with double safety systems and must be certified by competent bodies.
Dust Explosive Parameters
Dust does not have all the same characteristics. Before designing a system following the ATEX directive, it is necessary to consider some criteria, in particular the dust level of danger.
To do this, we can rely on two parameters:
- The “KST”, represents the dust deflagration index that gives an indication of the speed of expansion of the flames.
- The “PMAX”, represents the maximum pressure developed by the explosion of certain dust.
Atex Security Systems
There are some components that are more involved in the explosion, among them we find the explosion vents that break to allow the explosion to vent. A check is also necessary for internal components, however, which may have been damaged with the impact.
In the event of a deflagration, the system will have to be re-certified to ensure that it is still up to standard. Here are the safety systems established by the directive:
- Flameless Venting: helps to circumscribe the flame area by limiting damage and avoiding putting workers and the environment at risk.
- Explosion Suppression System: it can also detect hints of explosion and quickly suppresses them. If the explosion should occur, it is equipped with a sensor that warns the control center that opens the cylinders with the agent that allows suffocating the explosion in a few thousandths of a second.
- Safety Non-Return Valve: it is used to prevent the explosion from spreading in the suction line. In the event of an explosion, it blocks the aeriform flow by venting the explosion thanks to the other components.
- Explosion Diverters: divert the flow to allow the explosion to vent in a safe environment. Some diverters detect sparks and immediately signal the risk of bursting.
- Compartmental Shutters: they are of different types and compartmentalize the aeriform flow coming from the production departments. When the explosion occurs, they immediately isolate the affected area.
The Filters of Atex Systems
ATEX filters (bag filters) are equipped with explosion or flameless vents that open and vent the explosion, in this way the filter itself is prevented from exploding. They also withstand higher pressures than safety panels, precisely for this reason. Filters need to be designed according to the explosion pressure, which is determined by the dust used in production.
