Overview
IEC 60079-1:2014 - Edition 7.0, "Explosive atmospheres – Part 1: Equipment protection by flameproof enclosures 'd'" defines specific construction and test requirements for electrical equipment using the flameproof enclosure "d" type of protection for use in explosive gas atmospheres. This part supplements and modifies the general requirements of IEC 60079-0; where conflicts occur, IEC 60079-1 takes precedence. This edition (2014) supersedes the 2007 edition and includes subsequent corrigendum (June 2018) and an interpretation sheet (May 2020) incorporated in the text.
Key topics and technical requirements
The standard provides detailed, normative guidance on design, materials, verification and testing, including:
- Levels of protection (EPLs) - requirements for “da”, “db” and “dc” devices.
- Flameproof joints - required joint forms, widths and gaps for non-threaded, spigot, conical and serrated joints.
- Threaded and sealed joints - rules for threaded entries and restrictions related to thread forms; Clause 13 and Interpretation Sheet clarify permitted thread types and marking requirements.
- Entries for enclosures - requirements for threaded holes, cable glands, conduit sealing devices, plugs, sockets, bushings and blanking elements.
- Breathing and draining devices - dimensions, mounting, composition limits and tests for devices that form part of a flameproof enclosure.
- Materials and mechanical strength - material selection and strength verification for enclosures and internal components.
- Type, routine and acceptance tests - explosion pressure determination, overpressure tests, internal ignition non-transmission tests, thermal tests and tests specific to “dc” devices.
- Special topics - shafts/bearings, light-transmitting parts, fasteners, cemented and fused joints, and tests for enclosures with breathing/draining devices.
Important note from the Interpretation Sheet: Clause 13 restricts threaded entries for flameproof enclosures to metric and NPT threads to minimize thread-form mismatch. Thread adapters fitted and assessed as factory-assembled parts may use other forms (see Annex C).
Practical applications and users
IEC 60079-1 is essential for:
- Manufacturers and designers of electrical equipment intended for hazardous (gas) areas
- Test laboratories and certification bodies performing Ex testing and conformity assessment
- Safety and compliance engineers in oil & gas, petrochemical, chemical processing, mining, pharmaceuticals and utilities
- Procurement and maintenance teams specifying or servicing equipment used in explosive gas atmospheres
Related standards
- IEC 60079-0 (general requirements for equipment for explosive atmospheres) - this part is supplementary and takes precedence when in conflict.
- IEC 60079 series (other parts) - for complementary protection methods, installation, inspection and maintenance requirements.
Keywords: flameproof enclosure "d", explosive gas atmospheres, IEC 60079-1, flameproof joints, cable glands, Ex equipment, level of protection.