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.

EC directive 94/9/EC (ATEX95) - basis for equipment in the process industry

In the chemical and petrochemical industry, there are industrial processes which lead to explosive atmospheres. They are caused by, for example, gases, vapors or dust. Explosive atmospheres can also be anticipated in mills, silos, sugar and fodder factories due to the dust present there. Therefore, electrical devices in potentially explosive atmospheres are subject to special guidelines.

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").

Electrical equipment
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.

Associated equipment
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.

Process industry in potentially explosive areas

Group I:
Electrical equipment for firedamp areas (mines) which are susceptible to pit gases (methane) and/or combustible dusts (coal dust).

Group II:
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:

Ex protection table

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.

Temperature classes

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:

Zone 0:
Area in which hazardous explosive atmosphere is permanent, long-time or frequent. These conditions are usually present inside containers, pipelines, apparatus, and tanks.

Zone 1:
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.

Zone 2:
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):

Zone 20:
Area in which an explosive atmosphere consisting of dust/air mixtures is permanent, long-time or frequent.

Zone 21:
Area in which an explosive atmosphere consisting of dust/air mixtures is to be expected occasionally.

Zone 22:
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.