Abstract
In potentially explosive atmospheres — found in refineries, oil and gas platforms, chemical and pharmaceutical plants and grain-processing facilities — the electrical energy made available by field instruments may constitute an ignition source if not adequately limited. Intrinsic Safety (Ex i) is the protection technique that restricts the electrical and thermal energy of a circuit to levels below the minimum ignition energy of the atmosphere, rendering it incapable of producing a spark or heating sufficient to cause an explosion, even under fault conditions. This work presents a comprehensive technical description of intrinsic safety across the whole installation life cycle: area classification for gases and dusts, equipment groups and temperature classes, Equipment Protection Levels (EPL), entity parameters, design and validation of intrinsically safe systems, zener barriers and galvanic isolators, field wiring design rules, intrinsically safe fieldbus networks (FISCO and Power-i concepts) and, finally, the normative requirements for periodic inspection, preventive maintenance and repair of certified equipment. The systematization presented is based on the ABNT NBR IEC 60079 series and the corresponding international IEC standards, covering the process from circuit conception through to its field maintenance.