IEC 60079-31:2022

Overview

IEC 60079-31:2022 - "Explosive atmospheres - Part 31: Equipment dust ignition protection by enclosure 't'" specifies requirements for the design, construction, testing and marking of equipment and components protected by enclosure and surface temperature limitation for use in explosive dust atmospheres. It supplements and modifies the general requirements of IEC 60079-0 and takes precedence where the two conflict. This third edition (2022, with corrigendum October 2023 included) is a technical revision of the 2013 edition.

The standard applies to Ex Equipment and Ex Components using dust ignition protection by enclosure (“t”) and excludes:

• dusts of explosives that do not require atmospheric oxygen,
• pyrophoric substances, and
• equipment intended for underground mine workings or mine installations endangered by firedamp and/or combustible dust.

Key topics and requirements

• Levels of protection (ta, tb, tc) - defines protection levels, ingress protection relationship and related construction rules.
• Design & construction - requirements for joints, gaskets, threaded joints, windows, operating shafts, and supplementary internal enclosures to prevent dust ingress.
• Entries & cable transit devices - specific provisions for cable glands, cable transit devices and conduit sealing devices; Annex A adds supplementary requirements for entry devices (including cable transit).
• Electrical components & batteries - rules for cells and batteries (sealed cells required for many protection levels) and protection against overheating.
• Fault current and interrupting contacts - new/updated requirements for fault-current ratings; e.g., Ex equipment with Level "ta" limited to prospective short-circuit ≤ 1.5 kA; equipment intended to interrupt >10 kA must be tested and marked (major change C1).
• Temperature control & classification - determination of maximum surface temperature and updated malfunction/overload conditions for converter-fed rotating machines (major change C3).
• Verification & testing - type tests (including dust exclusion by enclosure), routine tests, and marking rules. Thermal tests for some aspects are referenced to IEC 60079-0.

Applications

IEC 60079-31 is used to ensure that electrical and non-electrical equipment placed in dust-hazardous industrial environments (mills, grain handling, food processing, chemical plants, metal powders, cement, etc.) do not ignite combustible dusts by hot surfaces, arcing or sparking. Typical equipment covered:

• motors, drives and control gear enclosed for dust protection
• lighting and instrumentation enclosures
• cable transit assemblies and entry devices
• battery-powered devices where sealed cells are required

Who should use this standard

• Equipment manufacturers and designers of Ex Equipment and Ex Components
• Test laboratories and certification bodies assessing dust-protected enclosures
• Electrical and safety engineers responsible for hazardous area installations
• Regulatory and compliance teams preparing technical documentation and marking

Related standards

• IEC 60079-0 (general requirements for explosive atmospheres) - this document supplements and modifies it.
• Other IEC 60079 series parts for specific protection concepts and hazardous-area practices.

Keywords: IEC 60079-31, explosive atmospheres, dust ignition protection, enclosure "t", Ex Equipment, dust atmospheres, cable transit, temperature class, fault current, sealed batteries.