Safety in industrial plants is of crucial importance, especially in areas with potentially explosive atmospheres. EX zones are special areas where there is an increased risk of explosions. Correct handling of these zones is essential to prevent accidents and ensure the safety of people and equipment. In this guide, you will learn everything you need to know about EX zones, their classification and the relevant ATEX directives.
Die ATEX-Richtlinien (ATmosphères EXplosibles) sind im europäischen Raum die wichtigsten Vorschriften zum Schutz vor explosionsfähigen Atmosphären. Sie setzen Anforderungen an Materialien, Gerätschaften und Arbeitsverfahren, um die Sicherheit in EX-Zonen zu gewährleisten. In ATEX Zonen müssen spezielle Sicherheitsvorkehrungen getroffen werden, um das Risiko von Explosionen durch gefährliche Atmosphären zu minimieren.
In this guide, you will learn everything you need to know about EX zones, their classification and the relevant ATEX directives in order to optimize your work in potentially explosive atmospheres.
Requirements for explosions
Before we turn to EX zones, it is important to understand what conditions are required for explosions. An explosion can only occur under certain conditions. The following elements must be present at the same time:
- brennbare Stoffe, die mit Luft eine explosionsfähige Atmosphäre bilden können
- Air or oxygen
- Ignition source
A explosive atmosphere occurs when air or oxygen mixes with flammable gases, vapors, mists or dusts - under normal atmospheric conditions. If such a mixture is ignited, the combustion spreads to all unburned material.
An area that is potentially at risk is considered potentially explosive if an explosive atmosphere can occur there. For an explosion to occur, the concentration of the flammable substance in the air must be within certain values, which are referred to as the "explosion range". This range varies greatly depending on the flammable substance in question.
The limits of the explosion range are defined by the lower explosion limit and the upper explosion limit. An explosion can only occur if the concentration of the flammable material is within these two limits. For example, an explosive atmosphere can occur inside a partially filled petrol tank, whereas a completely filled tank poses no risk as the upper concentration limit is exceeded here.
In commercial and industrial applications, various ignition ignition sources can occur, including
- Hot surfaces: These include, for example, radiators, hotplates, boilers and overheated machine parts.
- Flames and hot gases: Typical ignition sources include Bunsen burners, candles, matches and open heating systems with flames.
- Mechanically generated sparks: These are caused by friction or impact - for example when a hammer hits metal or when grinding materials.
- Electrical installations: Opening and closing electrical circuits, such as electric motors, can lead to ignition sources.
- Static electricity: These are discharge sparks that occur when charged parts are discharged by contact due to different voltage levels.
What are EX zones?
EX zones are specific areas in which an explosive atmosphere can occur and which therefore require special safety precautions. In order to regulate the use of electrical equipment in these zones, electrical equipment designed for use in potentially explosive atmospheres is divided into two main equipment groups:
- Group I: This includes electrical equipment used in underground areas where there is a risk of firedamp.
- Group II: This group refers to electrical equipment used in all other potentially explosive atmospheres. Within this group there is a further subdivision into three categories depending on the specific hazards.
Appliances in appliance group II are additionally marked with a letter indicating the state of the atmosphere:
- G - for areas in which explosive gas, vapor, mist or air mixtures are present
- D - for areas in which dust can form an explosive atmosphere with air
Equipment groups are used to classify electrical equipment according to the risk they pose in potentially explosive atmospheres. While the equipment groups define the type and safety precautions of the equipment, EX zones are specific areas in which such hazards can occur.
EX-Zonen werden basierend auf der Wahrscheinlichkeit und der Dauer des Auftretens einer explosionsfähigen Atmosphäre klassifiziert, beispielsweise in EX-Zone 0, EX-Zone 1 und EX-Zone 2. Diese Zonen geben detaillierte Auskunft darüber, wie und wo bestimmte Geräte eingesetzt werden dürfen, und spielen somit eine entscheidende Rolle für die Sicherheit im Umgang mit elektrischen Betriebsmitteln in explosiven Umgebungen.
Der wesentliche Unterschied zwischen EX-Bereichen und normalen Bereichen liegt in der Wahrscheinlichkeit der Zündung. In EX-Bereichen besteht ein höheres Risiko, während in normalen Bereichen das Explosionsrisiko nicht besteht oder stark minimiert ist. Für den sicheren Betrieb in EX-Zonen sind EX-geschützte Geräte unerlässlich, um das Risiko von Explosionen zu minimieren. Eine Ex-geschützte Lampe beispielsweise sorgt in EX-Zonen für eine sichere Beleuchtung und ist unerlässlich für den Explosionsschutz in gefährdeten Bereichen.
Overview of the different EX zones
EX zones are classified based on the probability and duration of the occurrence of an explosive atmosphere. They are typically divided into the following zones:
- EX Zone 0: Areas in which an explosive atmosphere is present continuously or for long periods of time.
- EX Zone 1: Areas in which an explosive atmosphere occasionally occurs.
- EX Zone 2: Areas in which an explosive atmosphere occurs only rarely or for a short time.
In addition, there are zones that are specifically designed for dust-forming environments:
- EX Zone 20: Areas in which an explosive dust atmosphere is present continuously or for long periods of time.
- EX Zone 21: Areas in which an explosive dust atmosphere occasionally occurs.
- EX Zone 22: Areas in which an explosive dust atmosphere occurs only rarely or for a short time.
Diese Zonen geben detaillierte Auskunft darüber, wie und wo bestimmte Geräte eingesetzt werden dürfen, und spielen somit eine entscheidende Rolle für die Sicherheit im Umgang mit elektrischen Betriebsmitteln in explosiven Umgebungen. Der HumiGuard® HT130 - Feuchtigkeitstransmitter für ATEX-Zonen ermöglicht beispielsweise zuverlässige Feuchtigkeitsmessungen und lässt sich problemlos in bestehende Anlagen integrieren.
The classification of the EX zones is decisive for the safety systems used in these areas. The ATEX Directive 1999/92/EC stipulates that every company must draw up an explosion protection document as part of the explosion protection document in which potentially explosive atmospheres are divided into zones.
Während EX-Zone 0 äußerst strenge Sicherheitsanforderungen stellt, gelten in EX-Zone 1 hohe Anforderungen, allerdings etwas weniger intensiv. In EX-Zone 2 sind die Anforderungen weniger rigide, da hier das Risiko für eine explosionsfähige Atmosphäre gering ist.
Bei den staubbildenden Zonen ergeben sich ähnliche Regeln: EX-Zone 20 und EX-Zone 21 erfordern hohe bis moderate Sicherheitsstandards, während in EX-Zone 22 weniger strenge Vorgaben gelten, da eine explosionsfähige Staubatmosphäre nur selten vorkommt.
It is important to note that the terms "frequently", "occasionally" and "rarely" do not have clear definitions. The relevant standards lack concrete figures. However, the following has become established in specialist circles:
- "Frequently" refers to more than 50 percent of the operating time.
- "Occasional" describes situations that may occur at irregular intervals, such as venting or sampling, and usually corresponds to 1 to 10 percent of the operating time.
In practice, you should assign the higher EX zone in case of doubt.
