IEC 60079-25-2020 Explosive atmospheres – Part 25: Intrinsically safe electrical systems

IEC 60079-25-2020 Explosive atmospheres – Part 25: Intrinsically safe electrical systems. 4 Descriptive system document A descriptive system document shall be created for all intrinsically safe systems. The descriptive system document shall include the technical justification for the combination of the apparatus 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 II and III), the Level of Protection and the Equipment Protection Level (EPL) for each part of the system, the temperature classification, and the ambient temperature rating in accordance with Clauses 5 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 with IEC 60079-1 1 ; f) the result of the assessment of intrinsically safe systems in accordance with Clause 1 2; and g) a unique document identification. The requirements found in Clauses 5 through 1 2 shall be used to determine the content of the descriptive system document. NOTE The descriptive system document is not the same as the control drawing referred to in IEC 60079-1 1 . Annex E shows an example of a typical diagram, illustrating the requirements of the descriptive system document. 5 Grouping and temperature classification Parts of intrinsically safe systems that are intended for use in an explosive atmosphere shall be grouped in accordance with the equipment grouping requirements of IEC 60079-0 and be assigned a temperature class or a maximum surface temperature in accordance with the temperature requirements of IEC 60079-0 and IEC 60079-1 1 . Associated apparatus not intended for use in an explosive atmosphere shall only be grouped in accordance with the equipment grouping requirements of IEC 60079-0. Where the intrinsically safe system or parts of the intrinsically safe system are specified as being suitable for operation outside the normal ambient temperature range of −20 °C and +40 °C, then this shall be specified in the descriptive system document. NOTE Different parts of the same intrinsically safe system can have different groups. The apparatus used can have different temperature classes and different ambient temperature ratings. 6 Levels of Protection 6.1 General Each part of...