Functional safety in ATEX and Safety devices in ATEX

In Europe, Safety devices for ATEX are under the scope of the harmonized standard EN 50495. The origin of this standard is the SAFEC project

In 1998, a pre-normative European project named SAFEC was launched in order to determine and classify these safety devices. Even though these safety devices were covered by the ATEX 94/9/EC Directive[1], they were subject to issues and different interpretations for their assessment by notified bodies and by manufacturers.

The results of this SAFEC project are today included into a Harmonized European standard: EN 50495 “Safety devices required for the safe functioning of equipment with respect to explosion risks” that came into force as a harmonized standard on 2010/09/17 for its first publication.

In order to precise the scope and the definition of these safety devices from the Directive[2], the application guide of the ATEX 94/9/EC Directive, since its second edition published in July 2005, incorporated the results of the SAFEC project in clause 3.10 “Safety, controlling or regulating devices as defined in Article 1.2”. A similar text has been incorporated in the new guide published, as the first edition of the ATEX 2014/34/EU Directive, in April 2016 within Clause 36 “Safety devices, controlling devices and regulated devices as defined in Article 1(1)(b)”.

EN 50495 standard applies to the manufacturers that put this kind of safety devices on the market, however, this standard is also for reference when equipment or protective systems require these safety devices but are put on the market separately. In this case the end user becomes a designer when he decides what kind of safety devices he implements in its applicative solution. For that purpose, the standard identifies and covers Safety devices that are classified in 2 types a) or b):

  1. devices, which are embedded as component in the equipment under control. The combined apparatus is considered as equipment.
  2. devices, which are installed separately from the equipment under control and considered as associated apparatus exclusively for a specific type of protection or specific equipment under control. The combined apparatus is considered as a system.

This is the situation for which end users have to select the safety level of the safety device.

 

[1] ATEX 94/9/EC directive that comes into force in July 2003

[2] Devices in the scope of Article 1.2

1. Safety devices, controlling devices and regulating devices, if they contribute to or are required for the safe functioning of equipment or protective systems with respect to the hazards of ignition or - respectively - with respect to the hazard of uncontrolled explosion are subject to the Directive;

2. These devices are covered even if they are intended for use outside the potentially explosive atmosphere. Those devices are not classified into categories according to Article 1.

3. Safety instrumented systems (e.g. a sensor, PLC and an actuator) in the sense of items 1. and 2. The whole system must be considered as a safety device in the sense of Article 1.2. Parts of this safety device may be located inside (e.g. a sensor) or outside (e.g. PLC) potentially explosive atmospheres.

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