IEC 60079-17 — Inspection and Maintenance of Ex Equipment Guide
IEC 60079-17 is the part of the IEC 60079 series that governs the inspection and maintenance of Ex electrical equipment in service. It is the primary reference standard for CompEx Ex03 and Ex04, and every inspection decision — what grade to use, how to classify a deficiency, when to take equipment out of service — is made with reference to IEC 60079-17.
Why Inspection Matters
Ex equipment is designed and certified to maintain its protection even if there is an internal ignition source. But this protection can be compromised by damage, corrosion, incorrect reassembly, or degradation over time. IEC 60079-17 provides the framework for detecting and addressing these issues before they create a risk of explosion propagation.
Inspection Grades
IEC 60079-17 defines three inspection grades:
Visual Inspection
Carried out without opening or disturbing equipment. Checks for obvious visible defects — physical damage, missing warning labels, paint on flamepaths, obvious corrosion, blocked ventilation. Can be carried out during normal operations without isolation.
Close Inspection
Includes all visual checks plus inspection that requires opening or accessing the equipment — checking cable gland thread engagement, examining terminal connections, opening enclosures to check internal condition. Typically requires isolation and permit to work.
Detailed Inspection
Includes all close inspection checks plus a full examination using tools and test equipment. Involves measuring flamepath gaps with feeler gauges, testing interlock switches, checking winding resistance of motors, and verifying all internal dimensions against the certificate requirements. Carried out less frequently than visual and close inspections.
Deficiency Categories — X, A, B, C
| Category | Meaning | Action |
|---|---|---|
| X | Protection compromised — immediate danger of ignition | Take out of service immediately. Do not restore until rectified. |
| A | Protection degrading — not immediate danger but must be rectified | Rectify at next scheduled maintenance opportunity |
| B | Minor issue — monitor and rectify within agreed timescale | Agree timescale with responsible manager. Note in records. |
| C | Note only — no immediate action required | Record in inspection documentation for awareness |
Category X deficiencies include: missing or loose bolts on Ex d equipment, open cable entries (unstoppered), flamepath gaps exceeding IEC 60079-1 limits, damaged or missing Ex e IP gaskets allowing moisture ingress, IS equipment with damaged barriers, and any condition where the fundamental protection mechanism is compromised. When in doubt — if the protection could fail — Category X.
Inspection Intervals
IEC 60079-17 does not mandate fixed inspection intervals — instead it requires that a schedule is established based on the equipment type, environment, and operating conditions. In practice, most operators use a risk-based approach with typical intervals of:
- Visual — monthly or quarterly (often incorporated into routine plant rounds)
- Close — annually or at each planned shutdown
- Detailed — every 3–5 years depending on equipment condition and environment
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