Recent Changes - Search:




edit SideBar

Equipmentand Protective Systems Directive

This Directive ("Equipment and Protective Systems intended for Use in Potentially Explosive Atmosphere", 94/9/ EC) applies to equipment and protective systems intended for use in potentially explosive atmospheres. It also applies to controlling devices and regulating devices intended for use outside potentially explosive atmospheres but required for or contributing to the safe functioning of equipment and protective systems with respect to the risks of explosion are also covered by the scope of this Directive.

Essential safety and health requirements given in the Annex 2 of the Directive are summarised below.

General requirements

  • Equipment and protective systems intended for use in potentially explosive atmospheres must be designed from the point of view of integrated explosion safety. In this connection, the manufacturer must take measures:
    • to prevent the formation of ATEX which may be produced or released by equipment and by protective systems themselves,
    • to prevent the ignition of ATEX (electrical and non-electrical source of ignition),
    • to halt the explosion immediately and/or to limit the range of explosion flames and explosion pressures to a sufficient level of safety.
  • Equipment and protective systems must be designed by taking ito account :
    • the potential operating faults,
    • special checking and maintenance,
    • and the surrounding area conditions.
  • All equipment and protective systems must be CE marked and be accompanied by appropriate instructions (particular with regard to safety).

Selection of materials

  • Used materials must neither trigger off an explosion, nor impair explosion prevention and protection.

Design and construction

Equipment and protective systems must be designed and constructed:

  • with due regard to explosion protection even for the components to be incorporated into or used as replacements in equipment;
  • so as to limit escapes of hydrogen or other flammable gases (enclosed structures, prevention of non-tight joints, flameproof enclosure systems, );
  • so as to withstand relevant external stresses;
  • so that, if the equipment and protective systems are in a housing or a locked container forming part of the explosion protection itself, it must be possible to safely open it;
  • so as to avoid injuries and high surface temperatures and to eliminate non-electrical hazards;
  • so to avoid dangerous overloading.

Potential ignition sources

  • Hazards arising from different potential ignition sources such as sparks, flames, electric arcs, mechanical sparks, hot spots, acoustic energy, optical radiation, electromagnetic waves, and other ignition sources must not occur.
  • Static electricity, stray electricity and leakage currents, overheatings, pressure compensation operations must not result in dangerous situations capable of ignite an ATEX.

Hazards arising from external effects

  • Equipment and protective systems must be capable of performing their intended function in full safety even when subjected to external stresses (environmental conditions, vibrations, thermal stresses, chemical stresses caused by aggressive substances, )

Safety-related devices

Essential requirements are given for the safety devices, such as:

  • The running of safety devices independently of any measurement or control devices required for the operation,
  • The rapid detection of any failure of a safety device,
  • The fail-safe principle for electrical circuits,
  • The direct connection between the safety-relate switching and the relevant control devices,
  • The security of the equipment and/or protective systems in case of safety device failure,
  • The incorporation of a safety factor on the alarm thresholds of devices with a measuring function.

Integration of safety requirements relating to the system

Essential requirements are given related to:

  • Automatic processes which deviate from the intended operating conditions,
  • Activation of the emergency shutdown system,
  • Power failure,
  • Connections,
  • Placing of warning devices as parts of equipment.

Supplementary requirements in respect of equipment

General requirements for equipment categories of equipment group IV are given in the table below.

Category 1Category 2Category 3
High probability of ATEX due to gases, vapours, mists or dustMedium probability of ATEX due to gases, vapours, mists or dustLow probability of ATEX due to gases, vapours, mists or dust
Very high level of protection for electrical and non electrical equipmentHigh level of protection for electrical and non electrical equipmentNormal level of protection for electrical and non electrical equipment

Detailed requirements for each category are given in the Annex 2 of the 94/9/EC Directive.

Supplementary requirements in respect of protective systems

  • Protective systems must reduce the effects of an explosion to a sufficient level of safety.
  • They must be designed so that explosions are prevented from spreading through dangerous chain reactions or flashover and incipient explosions do not become detonations.
  • In the event of a power failure, protective systems must retain their capacity to function for a period sufficient to avoid a dangerous situation.
  • Maximal pressure and temperature to be taken for the design of protective systems must be the one which can be expected during an explosion occurring under extreme operating conditions.
  • Protective systems such as pressure relief systems, explosion suppression systems, explosion decoupling systems must be designed so as to ensure their function whatever the size of the explosion.
  • Protective systems must be capable of being integrated into a circuit with a suitable alarm threshold so that, if necessary, there is cessation of product feed and output and shutdown of equipment parts which can no longer function safely.

<< Machinery Directive | Content | Pressure Equipment Directive >>

Edit - History - Print - Recent Changes - Search
Page last modified on December 03, 2008, at 12:10 PM