IEC 60079-25:2020 pdf free.Explosive atmospheres – Intrinsically safe electrical systems.
A descriptive system document shall be created for all intrinsically safe systems. Thedescriptive system document shall include the technical justification for the combination of theapparatus and shall include at a minimum the following:
a) a block diagram of the system listing all the items of apparatus within the system including simple apparatus and the interconnecting wiring;
b) a statement of the equipment Group subdivision (for equipment Groups ll and Il), the Level of Protection and the Equipment Protection Level (EPL) for each part of the system， thetemperature classification, and the ambient temperature rating in accordance with Clauses5 and 6;
c) the requirements and permitted parameters of the interconnecting wiring in accordance with Clause 8;
d) details of the earthing and bonding points on which intrinsic safety depends;
e) where applicable，the confirmation of apparatus as simple apparatus in accordance withIEC 60079-11;
f) the result of the assessment of intrinsically safe systems in accordance with Clause 12; andg) a unique document identification.
The requirements found in Clauses 5 through 12 shall be used to determine the content of thedescriptive system document.
NOTE The descriptive system document is not the same as the control drawing referred to in IEC 60079-11.Annex E shows an example of a typical diagram, illustrating the requirements of the descriptivesystem document.
Parts of intrinsically safe systems that are intended for use in an explosive atmosphere shallbe grouped in accordance with the equipment grouping requirements of lEC 60079-0 and beassigned a temperature class or a maximum surface temperature in accordance with thetemperature requirements of lEC 60079-0 and lEC 60079-11.
Associated apparatus not intended for use in an explosive atmosphere shall only be grouped inaccordance with the equipment grouping requirements of lEC 60079-0.
Where the intrinsically safe system or parts of the intrinsically safe system are specified asbeing suitable for operation outside the normal ambient temperature range of -20 C and+40C, then this shall be specified in the descriptive system document.
NOTEDifferent parts of the same intrinsically safe system can have different groups. The apparatus used can havedifferent temperature classes and different ambient temperature ratings.
Each part of an intrinsically safe system intended for use in an explosive atmosphere shall haveaLevel of Protection “ia” , ib” or “ic” in accordance with lEC 60079-11 and an EPL in accordancewith lEC 60079-0.Separate parts of the system may have a different Level of Protection orEPL.IEC 60079-25 pdf download.