Maintenance' (IEC 60079-17) purpose is to preserve the original explosion-protection integrity. Nothing is changed—only checked, cleaned, tightened, adjusted, or replaced like-for-like. Maintenance keeps the equipment within its certified condition.

Repair' (IEC 60079-19) purpose is to restore explosion-protection integrity after it has been compromised. Something has failed, degraded, or been damaged → intervention affects Ex-critical features. Repair addresses the Ex protection concept itself.

IEC 60079-17 — Maintenance in Ex terms

What is maintenance?

Examples:

• Visual / close / detailed inspections
• Cleaning dust, dirt, corrosion (without material removal beyond limits)
• Tightening terminals
• Replacing seals, gaskets, fasteners exactly as specified
• Replacing components identical in type, rating, material
• Functional checks

What maintenance is not allowed to do:

• No dimensional changes
• No material substitution
• No enclosure machining
• No change to creepage/clearance, flamepaths, IP rating, thermal behavior

Competence level required is an Ex-trained personnel, shall be familiar with protection types (Ex d, e, i, t, etc.) and no(!) manufacturer-level authority required. Maintenance is part of operator's duty of care, ongoing compliance and IEC 60079-17 inspection regime

Note: 1) No re-certification required 2)No manufacturer responsibility triggered

IEC 60079-19 — Repair in Ex terms

What automatically becomes a repair as per the moment you touch any Ex-critical feature, you are in 60079-19 territory.

Examples:

• Flamepath damage or resurfacing (Ex d)
• Welding or brazing on enclosures
• Rewinding motors
• Replacing encapsulation (Ex m)
• Modifying terminals, bushings, cable entries
• Changing thermal paths
• Replacing parts without exact original specification
• Any action that could affect T-class, EPL, IP, ignition protection

Repair is NOT "advanced maintenance". IEC is very explicit here - repair is not an extension of maintenance – it is a controlled reconstruction activity.

Competence & authorization

• Repair facility must be:
• Technically Ex competent personell
• Properly equipped
• Working to documented procedures (audited by 3rd party)
• Often requires:
• Manufacturer data
• Repair records
• Post-repair verification

Legal meaning

• Responsibility partially shifts toward the repair organization
• Traceability becomes mandatory
• Documentation must survive audits and incidents

Note: 1) erification is mandatory 2) Improper repair = loss of Ex conformity

A very useful field rule:

If the Ex marking would still be unquestionably valid without explanation → maintenance

If you need to explain what you did → repair

Or even simpler:

• No change, only preservation → IEC 60079-17
• Any restoration after degradation → IEC 60079-19

5. Responsibility & liability difference (this is where accidents happen)

Most real explosions linked to "maintenance" failures are actually undocumented repairs.

-               Many catastrophic Ex failures came from well-intended repairs

-               People thought they were "just fixing"

-               Ex protection is non-intuitive (microns, materials, heat paths, tolerances)

Maintenance maintains conformity. Repair recreates conformity – and must prove it.

Keep up the good work!

Arpad
veress@exprofessional.com