ATEX zone and risk of explosion
To prevent the risk of explosion, it is the employer's responsibility to set up a prevention action plan. This plan includes measures to eliminate or control sources of ignition, when the formation of an explosive atmosphere, also called an ATEX Zone, could not be avoided.
1. What is an ATEX zone?
One of the essential steps in the process is the zoning of explosion hazard areas. This zoning attempts to describe the probability of an explosive atmosphere forming and to quantify its mass.
These hazardous locations are classified into risk zones, depending on the frequency and duration of the explosive environment.
Depending on the technical and organizational precautions applied, and their durability, the zoning may be less restrictive.
Installations or locations likely to have one or more ATEX zones are marked with the regulatory symbol.
1.1 Characterization of the ATEX zone (danger and extent)
The purpose of ATEX zoning is to define the risk and to match the equipment to be used by zone.
The head of the establishment or his collaborators must determine the risk of explosion on a site in the presence of gases, vapors or dusts.
There are 3 levels of ATEX Zone classification depending on the degree of ventilation of the fuel source and the nature of the ventilation in the Zone. There is a difference between gas/vapour zones and dust zones.
1.2 Examples of gas/vapour zone locations
> In general, a zone 0 will be the inside of tanks, pipes, etc.
> A zone 1 may include :
- the immediate vicinity of zone 0
- the immediate proximity of supply openings, sampling or purge valves, filling and emptying openings, etc.
- low points of the installations (retention pits, gutters)
> A zone 2 may include :
- locations surrounding zones 0 and 1
- Areas in close proximity to flanges, connections, valves and pipe fittings, glass level tubes, appliances made of fragile materials, or other equipment that may leak
1.3 Examples of dust zone locations
> A zone 20 corresponds to the inside of tanks, pipes, containers, as well as a zone 0 for gases/vapors.
> A zone 21 may include :
- locations in the immediate vicinity of powder filling or emptying points
- locations in which dust layers appear and are likely, during normal operation, to lead to the formation of a cloud of combustible dust of sufficient concentration mixed with air.
> A zone 22 may include :
- locations in the vicinity of devices, protective systems and components containing dust, from which dust can escape in the event of a leak and form dust deposits
2. Ignition sources: definition and guide to suppress or control them
2.1. What is an ignition source?
If the presence of ATEX zones cannot be avoided, then the sources of ignition must be eliminated or at least controlled. This is an integral part of the prevention plan.
An ignition source is a source of energy that can cause an explosion in an ATEX Zone. There are several types of ignition sources:
- Hot surfaces
Generally, ignition sources are differentiated according to their origin: electrical, mechanical, thermal, electrostatic, climatic, etc.
In ATEX zones, it is therefore essential to eliminate ignition sources in order to avoid the risk of explosion. For this, it is necessary to anticipate and give precise rules. It is also important to monitor operations that generate flames, sparks and hot surfaces. These operations are called hot spot work and require a fire permit. On the other hand, it is necessary to put in place specific equipment that will be ATEX certified. These devices are subject to a CE or Ex regulatory marking.
2.2 How to suppress or control sources of ignition?
This preventive action consists first of all in removing from the ATEX zone the equipment that does not need to be there. Then, different measures can be implemented:
> Act on the processes by setting up:
- Safety systems so as not to exceed defined thresholds of temperature, pressure, etc.
- Cooling systems to prevent chemical reactions or overheating
> To carry out controls thanks to :
- Temperature and pressure detectors, etc.
- Carbon monoxide detectors
- Regular control of electrical installations
> Act on the appliances:
- Adapt the equipment to the classification of the ATEX zone
- Use mobile tools that do not cause sparks
> Implement organizational measures:
- Have a fire permit for employees working with hot spots
- Limit the number of workers present in an ATEX zone
- Provide workers with work clothes that allow electrostatic charges to flow
- Train workers to work in ATEX zones
3. Maintenance in ATEX zones
When an intervention must take place in an ATEX zone, the necessary maintenance or servicing must first be subject to a risk analysis and the establishment of several documents (prevention plan, fire permit, etc.). Following these analyses, a specific zoning can be set up for the technical intervention, since it can be carried out near an ATEX zone, or even generate one.
During an intervention, the activity conditions are not always those of normal operation. Indeed, they can be voluntarily degraded, in order to test the correct operation of gas detection devices for example. It will therefore be essential to correctly identify the risks of the intervention, to eliminate if possible the ATEX zones present (for example by closing all or part of the installation) and to be attentive to the remaining zones or those created by a specific zoning.
For regular maintenance or servicing, it is important to take into account these specific ATEX zones and to include them in the zoning.
> Training for interventions in ATEX zones
Training your employees is a key issue for you in order to ensure the health of your workers. The ATEX training aims to :
- Evaluate the risks and implement an ATEX approach.
- Identify ATEX zones.
- Choose and maintain ATEX equipment
To work in ATEX zones, it is mandatory for employees to have an ATEX authorization corresponding to the level of danger of the zone in which they are going to operate as well as the type of equipment used (electrical or mechanical).
Training your employees to work in ATEX zones is an obligation, in the same way, our technicians at BE ATEX pass authorizations to intervene safely for you, but also for them.
At BE ATEX, our teams are accredited by organizations to work in ATEX zones. The ISM ATEX or Installation, Service and Maintenance of Electrical Installations in ATEX certification allows our teams to intervene in the design, implementation and/or maintenance of electrical installations in explosive atmospheres.
An ATEX training is :
- Acquiring basic knowledge for personnel working or circulating in ATEX zones
- Raising awareness of explosive risks among the personnel concerned
- Enabling agents to intervene in these zones
- Work safely on electrical and mechanical installations in explosive environments
- Identify areas at risk of explosion