Overview
IEC 60079-25:2020 (with Amendment 1 consolidated) specifies the design, construction and assessment of intrinsically safe electrical systems (Type of Protection “i”) intended for use in locations requiring Group I, II or III explosion-protected equipment. This edition supersedes the 2010 edition, incorporates corrigenda and technical revision material, and takes precedence where it conflicts with IEC 60079-0 or IEC 60079-11. Installation requirements for Group II/III systems designed to this standard are given in IEC 60079-14.
Key topics and requirements
- Scope and applicability: Systems intended for explosive atmospheres in mining (Group I), surface industries (Group II) and combustible dust environments (Group III).
- Levels of protection: Definitions and requirements for ia, ib and ic intrinsic safety levels.
- System documentation: Requirement for a descriptive system document that records system parameters, limitations and interconnections.
- Cable and wiring rules: Guidance for interconnecting wiring, single- and multi-circuit cables, dielectric strength, screens and defined Type A/B/C cable classifications.
- Assessment methods: Procedures for assessing systems containing apparatus certified to IEC 60079-11 and apparatus not separately evaluated; methods for single and multiple power-source systems.
- Electrical parameters: Assessment and verification of capacitance, inductance, L/R, and inductive parameters; adjustments for unspecified parameters and combined lumped effects.
- Enclosures, earthing and bonding: Requirements for enclosures and grounding practices specific to intrinsically safe systems.
- Fault conditions and testing: Assessment of faults in multi‑circuit cables, type verifications and type tests.
- Predefined/recognized systems and schemes: Normative/informative annexes covering FISCO, 2‑WISE, simple apparatus use, predefined systems and worked examples for system verification.
Practical applications and users
Who uses IEC 60079-25:
- Design engineers and system integrators developing intrinsically safe control systems and fieldbus networks.
- Manufacturers of intrinsically safe apparatus and multicore cables.
- Certification bodies and notified testing labs performing system assessments and type tests.
- Installation/maintenance personnel and safety engineers in hazardous industries.
Typical industries and applications:
- Oil & gas, petrochemical and chemical plants; mining and tunnelling (Group I); grain handling, pharmaceuticals and food processing where combustible dust (Group III) is present; process control, instrumentation and field communication networks requiring intrinsic safety.
Related standards
- IEC 60079-0 - General requirements for explosive atmospheres
- IEC 60079-11 - Intrinsic safety “i” for apparatus
- IEC 60079-14 - Installation requirements for electrical installations in explosive atmospheres
- IEC Electropedia - terminology reference
Keywords: IEC 60079-25:2020, intrinsically safe, explosive atmospheres, intrinsic safety, Type of Protection i, FISCO, 2‑WISE, Group I II III, IEC 60079-11, IEC 60079-14.
