ATEX
Every operator who wants to measure the temperature of explosive substances with Pt100 resistance thermometers, has already dealt with the subject of “explosion protection” and has come across the term ATEX.ATEX is an abbreviation of the French term Atmosphères exlosibles (explosive atmospheres).
ATEX is mainly based on 2 directives that are legally binding in the European Union.
- ATEX Directive 2014/34/EU
This defines the obligations of manufacturers of products for potentially explosive atmospheres.
Manufacturers must ensure that their devices have the properties required for explosion protection.
The devices are marked accordingly and a declaration of conformity guarantees the operator in which areas (mining or above ground) and for which type of substances (gas/vapor/dust) the devices may be used.
Furthermore, the safety level (very high/high/increased) of the devices is specified and how explosive the substance to be measured may be (explosion group/ignition temperature, defined by the maximum surface temperature of the devices). For details, see labeling of the devices.
Link to Directive 2014/34/EU
- ATEX Directive 1999/92/EG
This operating guideline regulates the obligations of the system operator and is intended to protect persons working in a potentially explosive atmosphere.
The operator must prepare a risk assessment of his system, which includes, for example, the classification of the explosion protection zones and the determination of the relevant substance data for the explosive substances used.
Main objectives for preventing an explosion:-
Prevention/reduction of an explosive atmosphere.
e.g.: use other substances, extraction, protective gas atmosphere -
Avoidance of ignition sources.
e.g.: Appliances with a lower surface temperature - If an explosion does occur.
Reduce the impact of the explosion to a level that is as harmless as possible. e.g.: Structural measures such as explosion flaps.
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Prevention/reduction of an explosive atmosphere.
Explosion protection zones
Areas with potentially explosive atmospheres, also known as explosion protection zones, occur
wherever flammable substances in the form of gases, vapors, mists or dusts can occur in hazardous
concentrations. These play a central role when working with flammable substances.
In order to minimize risks for people, systems and the environment, explosion protection zones
are divided into different categories, each of which requires different safety requirements.
The classification is based on the probability and duration of the occurrence of a hazardous
explosive atmosphere.
This systematic classification is the basis for the selection of suitable protective measures,
such as explosion-proof devices and safety-conscious operating procedures, and ensures
operational safety in potentially hazardous environments.
The terms “frequently, constantly” are not defined in the DIN standard.
It is generally agreed that this is the case if an explosive atmosphere is present for more than 50% of the operating time of a system.
This applies, for example, inside pipes and containers.
The term “occasionally” is not defined in the DIN standard.
It has generally been agreed that this is the case when an explosive atmosphere occurs at irregular intervals and does not exceed a period of 1 to 10% of the operating time of the system.
This is the case, for example, in the immediate vicinity of zone 0 if samples are taken occasionally or the system is vented.
The terms “rare, short-term” are not defined in the DIN.
It has generally been agreed that this is the case if an explosive atmosphere is present for less than 1 to 10 hours per year.
This is normally only the case due to faults and is not normally to be expected during normal operation.