Light emitting diodes (LED) for installation in zone 1: A feasible procedure to determine the equivalent protection level

In recent years, first devices with LED light sources appeared in the Ex's world. Even if LEDs technology require higher purchase costs than traditional sources, from the technical point of view, there are advantages that can offset this initial high cost. The most important are: low power consumption, that allow both electrical energy savings and installation of small section cables and lower protection; high number of operating hours, that permit save on the cost of maintenance and on the hourly cost of the LED lamp. The draft of the standard IEC/EN60079-7 explicitly excludes LED sources from the set of EPL b components for the lack of an adequate knowledge of failure phenomena. By taking into consideration the numerous technical and economic advantages that LED sources provide to the Ex world, the proposed study aims to evaluate the reliability of the LED technology in order to determine the safety integrity through knowledge of LED failure rates and failure modes. The line that we intend to adopt collects the instruments required in assessing SIL for equipment according to the IEC/EN61508, which has already been adopted for a number of equipment, components and sub-systems used in the field of functional safety. It is well known that some devices can be used as active control of dangerous sources, with a real and expected level of reliability, if they have been qualified according to the IEC/EN61508. Further proof of what expressed above is the ATEX European harmonized standard EN50495: 2010, which defines the integrity level of the functional safety of active control systems and compares it with the level of fault tolerance of the Equipment Under Control (EUC).