IEC 60079-28:2015

Overview

IEC 60079-28:2015 - Explosive atmospheres - Part 28 - Protection of equipment and transmission systems using optical radiation - specifies requirements, testing and marking for equipment that emits optical radiation intended to be used in or to transmit radiation into explosive atmospheres. The edition includes Interpretation Sheet 1 (2019) clarifying applicability with IEC 60079-0. The standard covers Groups I, II and III and Equipment Protection Levels EPLs Ga, Gb, Gc, Da, Db, Dc, Ma and Mb.

The standard excludes ignition by ultraviolet radiation, ignition by absorption in the explosive mixture itself, and devices such as explosive absorbers or catalytic absorbers that contain their own oxidizer.

Key topics and requirements

• Scope and applicability - laser equipment, optical fibre equipment and other convergent light sources where light is focused into the hazardous area; and explicit exceptions (e.g., Class 1 lasers per IEC 60825-1 and divergent sources).
• Types of protection - concepts and design requirements for:
  • inherently safe optical radiation (op is),
  • protected optical radiation (op pr),
  • optical systems with interlock for fibre breakage (op sh).
• Risk levels and EPL mapping - relationship between ignition risk, EPL and suitable protection measures.
• Ignition testing and type verification - test set-up, reference tests, ignition criteria, mixtures, safety factors and specific pulse/continuous-wave test procedures.
• Enclosure protection and exclusions - use of flameproof “d”, pressurized “p”, restricted breathing “nR”, dust protection “t”, or minimum ingress protection IP6X to prevent ingress of absorbers.
• Marking and documentation - required marking information for certified equipment.
• Annexes - ignition mechanisms, optical fibre cable design, ignition hazard assessment and alternative risk assessment methods.

Practical applications

IEC 60079-28 is applied where optical equipment could present an ignition source in hazardous locations:

• Laser systems, fibre-optic transmitters and receivers used in oil & gas, petrochemical, chemical processing and mining.
• Optical inspection, sensing, communication (fibre links) and laser-based measurement equipment installed in Zone/Division hazardous areas.
• Design and certification of intrinsically safe optical modules, optical fibre assemblies and protective enclosures.

Who should use this standard

• Manufacturers of lasers, fibre-optic equipment and optical transmitters intended for explosive atmospheres.
• Design and safety engineers specifying equipment for hazardous locations.
• Certification and conformity assessment bodies, test laboratories and ExCB/ExTL assessors.
• Plant operators, integrators and maintenance teams implementing safe optical systems in explosive environments.

Related standards

• IEC 60079-0 (general requirements for Ex equipment)
• IEC 60825-1 (laser safety classification)
• IEC 60079 series standards for specific Types of Protection (e.g., IEC 60079-1, -2, -15, -31)

Keywords: IEC 60079-28, optical radiation, explosive atmospheres, laser safety, optical fibre, inherently safe optical, EPL, ignition testing, types of protection.