IEC 60079-6:2015

Overview

IEC 60079-6:2015 is an international standard developed by the International Electrotechnical Commission (IEC) that specifies the requirements for equipment protection by liquid immersion ("o") in explosive gas atmospheres. This standard addresses the design, construction, testing, and marking of explosive atmosphere (Ex) equipment and components using the liquid immersion method, ensuring optimal safety in hazardous environments. It introduces key protection levels-"ob" and "oc"-and revised specifications to enhance reliability and safety.

The fourth edition of IEC 60079-6 constitutes a major technical revision, expanding the scope from oil immersion specifically to liquid immersion, updating requirements, and incorporating protections for sparking contacts. It supersedes previous editions, modifies general IEC 60079-0 provisions where conflicting, and adds new testing and marking protocols to ensure conformity.

Keywords: IEC 60079-6, liquid immersion "o", Ex equipment, explosive atmospheres, equipment protection, hazardous areas, EPL Mb, EPL Gb, electrical safety, protective liquid, sparking contacts.

Key Topics

• Scope and Applicability:
  IEC 60079-6 applies to Ex equipment and components designed for use in explosive gas atmospheres, protected by immersion in a liquid barrier. It covers two protection levels:

  • Level "ob" (Equipment Protection Level EPL "Mb" or "Gb"), for rated voltages up to 11 kV r.m.s.
  • Level "oc" (EPL "Gc"), for rated voltages up to 15 kV r.m.s.
    For equipment rated beyond 15 kV and up to 245 kV, supplementary requirements are detailed.

• Design and Construction Requirements:
  The standard mandates careful consideration of enclosure design to contain liquid, provisions for sealing or controlled ventilation, electrical clearances, creepage distances, and immersion depth. It also covers devices for liquid level indication and safety systems for maintaining protective liquid integrity during operation.

• Protective Liquid Specifications:
  Detailed requirements concern the type, volume, and quality of the protective liquid, including flashpoint limits and contamination management. The liquid must reliably prevent ignition sources from contacting explosive atmospheres while maintaining electrical insulation.

• Switching Device Protection:
  IEC 60079-6 specifies how switching devices must be adequately protected via immersion, emphasizing the capability to safeguard sparking contacts under both "ob" and "oc" levels of protection.

• Testing and Verification:
  Rigorous type and routine tests are prescribed, including overpressure, reduced pressure, switching operations, and maximum temperature withstand tests to verify compliance with safety objectives.

• Marking and Documentation:
  The standard requires clear and durable markings on equipment to indicate protection type and level, rated voltage, and other essential safety information, along with comprehensive operating instructions and maintenance guidelines.

Applications

• Industrial Process Plants:
  Use of equipment compliant with IEC 60079-6 is especially critical in chemical plants, oil refineries, and gas processing facilities where explosive gas atmospheres may be present. Liquid immersion protection offers a reliable barrier against ignition sources in such hazardous zones.

• Electrical Equipment in Hazardous Locations:
  Motors, connectors, switches, and control devices designed with liquid immersion "o" protection ensure operational safety and reduce risk of explosions due to electrical arcs or sparks.

• High Voltage Equipment:
  Equipment operating up to 15 kV (and provisions for up to 245 kV) benefits from this standard, enabling safe operation of power distribution and control apparatus using liquid immersion as protective means.

• Maintenance and Inspection:
  The standard provides requirements for maintenance and overhaul, facilitating extended equipment lifecycle and operational safety through regular inspection of liquid quality and containment integrity.

Related Standards

• IEC 60079-0: General requirements for electrical equipment in explosive atmospheres. IEC 60079-6 supplements and, where conflicting, takes precedence over IEC 60079-0.

• IEC 60079 Series: Includes other parts covering various protection techniques such as flameproof enclosures (d), intrinsic safety (i), and increased safety (e).

• ISO/IEC Directives, Part 2: Guidelines on drafting International Standards ensure consistent structuring and technical clarity in IEC 60079 series publications.

By adhering to IEC 60079-6:2015, manufacturers and users of Ex equipment can ensure enhanced safety, performance, and compliance when deploying liquid immersion protection methods in explosive gas atmospheres. This standard is vital for minimizing ignition risks and maintaining operational integrity in hazardous industrial environments.