Safety using ex products from Phoenix Contact
The 94/9/EC (ATEX95) EC directive is an important basis for equipment in the process industry. All our equipment has already been approved as per this directive in 1997.
Devices and protection systems in potentially explosive areas
The 94/9/EC directive of the European Parliament dated 23/03/94 (ATEX manufacturer directive) is of particular importance in the field of CENELEC (European Community and Western European EFTA states). It serves in facilitating the adaptation of the legal provisions of the member states of the European Union for devices and protection systems for correct use in potentially explosive areas. The 94/9/EC directive must be applied to all explosion-protected devices and protection systems brought into the market in Europe. The scope of this directive also includes safety, control and regulating devices which are used outside potentially explosive areas, but which are necessary for, or contribute in, safe operation of devices and protection systems with respect to explosion hazards.
The term devices includes machines, operational equipment, stationary or mobile devices, control parts and system accessories. This term is also used for warning and prevention systems which are determined, either individually or combined, for the generation, transmission, storage, measurement, control and conversion of energy and for processing materials and which have the potential to ignite and cause an explosion.
Protection systems are devices designed to immediately stop an approaching explosion and/or restrict the area affected by the explosion. They are put into operation separately as autonomous systems.
Components are parts that are necessary for operating the devices and protection systems, but do not carry out an autonomous function. European directives are implemented in ordinances or laws at the national level.
Systems in potentially explosive areas
The 1999/92/EC directive (ATEX operator directive) was issued in Europe to regulate the operation of systems in potentially explosive areas.
Terms from the ex area - explosive atmosphere
A mixture of combustible gases, steam, vapors or dust and air in atmospheric conditions in which combustion can extend to the entire unburnt mixture after igniting.
Potentially explosive area
An area in which the atmosphere may be potentially explosive due to local or operational conditions ("Ex area").
All components, electric circuits or parts of electric circuits that are usually located in one housing.
Intrinsically safe electrical equipment
Electrical equipment in which all circuits are intrinsically safe. Note: This equipment may be used directly in the Ex area.
Electrical equipment that contains both intrinsically safe and non-intrinsically safe circuits and is designed in such a way that the non-intrinsically safe circuits cannot influence the intrinsically safe ones. Note: Associated electrical equipment may not be used directly in potentially explosive areas without additional protection defined by a protection type.
Classification in groups
The general regulations included in EN 60079-0 (old: EN 50014) classify the electrical equipment for potentially explosive areas into two groups.
Electrical equipment for firedamp areas (mines) which are susceptible to pit gases (methane) and/or combustible dusts (coal dust).
Electrical equipment for potentially explosive areas, excluding mines susceptible to firedamp. This includes, among other things, equipment for the chemical, petrochemical, pharmaceutical industries and waste water treatment as well as equipment for the food industry (mills, silos). The protection types Exi, Exd and Exn are further divided into gas groups, here on the basis of intrinsic safety:
The classification for the intrinsic safety protection type is based on the minimum ignition energy of the gas or vapor.
Classification in temperature classes
Dividing the various gases into explosion or gas groups according to their minimum ignition energy is not sufficient to describe the gases adequately with respect to their explosive properties. A gas can be caused to explode either when the ignition energy is exceeded or where there is an excessively high temperature caused by a hot surface. However, this ignition temperature is not always linked to the ignition energy, i.e. a gas with low ignition energy does not necessarily explode at a low temperature.
Electrical equipment that is used directly in potentially explosive areas is therefore divided into temperature classes. Temperature classes define the maximum surface temperature even in the case of errors. Parallel to this, the gases are classified according to the different ignition temperatures.
Division into zones
Potentially explosive areas are classified in zones according to the probability of their occurrence. The EN 60079-10 standard defines the zones for the explosive gas atmosphere area as follows:
Area in which hazardous explosive atmosphere is permanent, long-time or frequent. These conditions are usually present inside containers, pipelines, apparatus, and tanks.
Area in which hazardous explosive atmosphere is to be expected occasionally during normal operation. This includes the immediate surroundings of zone 0, as well as the areas close to filling and discharge plants.
Area in which hazardous explosive atmosphere is not expected during normal operation and even if it occurs, it is only for a short time. Zone 2 includes storage areas if they are only used for storage, areas around pipe connections that can be disconnected and generally the areas near Zone 1.
Areas that are potentially explosive as a result of combustible dusts are classified into the following zones in accordance with EN 61241-14 (old: EN 50281-1-2):
Area in which an explosive atmosphere consisting of dust/air mixtures is permanent, long-time or frequent.
Area in which an explosive atmosphere consisting of dust/air mixtures is to be expected occasionally.
Area in which an explosive atmosphere caused by swirled up dust is not to be expected and even if it occurs, then in all probability it will occur rarely and for a short time.
The ATEX directive assigns devices for use in potentially explosive areas to categories. In the IEC 60079-0, the term "Equipment Protection Level (EPL)" is used for category. There are three different device categories corresponding to the different zones. They are categories M1 and M2 for Group 1 and categories 1, 2 and 3 for Group II.
The categories for device group II are described in more detail below:
Devices designed to guarantee a very high degree of safety. Devices in this category must guarantee the required degree of safety even in the rare cases of device failure and therefore be provided with explosion protective equipment, so that
- in the case of failure of one installation safety equipment, there is at least a second, independent installation safety equipment which guarantees the necessary safety, or
- that the necessary safety is guaranteed when two independent errors occur.
Devices designed to guarantee a high degree of safety. The installation safety equipment for explosion of this category guarantees the necessary degree of safety, even in the case of frequent device failure or common errors.
Devices designed to guarantee the standard degree of safety. Devices in this category guarantee the necessary degree of safety in normal operation.
Assignment of categories to zones according to the 94/9/EC directive:
In Europe, the standards from the series of standards EN 50014 ff have been adopted in EN 60079 ff. Hence, even the identification has been modified: EEx -> Ex.
Please note that: Devices/components with the old identification (EEx) may be combined with those having the new identification (Ex).