IEC 60079-17 Best Practices: What to Check During Inspection and Maintenance of Ex Equipment
Practical IEC 60079-10-1 best practices for hazardous area classification, from identifying release sources and ventilation to avoiding common field mistakes.
Maintaining explosion-protected electrical equipment is not simply a matter of checking whether the equipment is still operating. In a hazardous area, the condition of the equipment and its installation can directly affect the protection concept on which the installation relies.
IEC 60079-17 provides requirements and guidance for the inspection and maintenance of electrical installations in explosive atmospheres. In practice, however, inspection teams need to look beyond whether equipment is present and operational. They need to determine whether the equipment, enclosure, cable entries, connections, and other installation details remain in an acceptable condition.
This article focuses on practical inspection and maintenance checks that can help identify problems before they develop into a loss of explosion protection or an unexpected shutdown.
1. Start With the Equipment and Its Ex Protection Concept
Before inspecting an Ex installation, identify the protection concept used by the equipment.
Different types of explosion protection have different characteristics and inspection considerations. For example, the checks applicable to an Ex d enclosure are not necessarily the same as those applicable to Ex e or other protection concepts.
Review the equipment marking and identify the relevant protection concept before beginning the inspection.
Best practice: Do not use one generic inspection approach for every type of Ex equipment. The inspection should consider how the particular protection concept is intended to prevent ignition.
2. Check the Equipment for Physical Damage
Physical damage is one of the easiest problems to identify during an inspection, but it can also be overlooked when the equipment is still functioning normally.
Look for:
- Cracks or damage to enclosures
- Deformation caused by impact
- Corrosion
- Damaged covers
- Missing or damaged fasteners
- Damaged cable entries
- Signs of overheating
- Other deterioration that could affect the protection of the equipment
Best practice: Do not consider equipment acceptable simply because it is energized and operating. The physical condition of the equipment is part of the inspection.
3. Pay Particular Attention to Ex Enclosures
The enclosure is an important part of many explosion protection concepts. Its condition should therefore receive more attention than a normal visual inspection of electrical equipment.
Check the enclosure surfaces, covers, joints, fasteners, and other components that contribute to maintaining the intended protection.
For equipment where the enclosure integrity is critical to the protection concept, damage, unauthorized modification, or incorrect assembly can be particularly significant.
Best practice: Compare questionable conditions against the manufacturer's documentation and applicable certification rather than making assumptions based only on appearance.
4. Inspect Cable Glands and Cable Entries
Cable entries are often exposed to mechanical stress, vibration, environmental conditions, and maintenance activities.
During inspection, check whether:
- The gland is correctly installed
- The gland is compatible with the cable
- The gland remains secure
- There are signs of damage or deterioration
- Unused entries are correctly closed
- Sealing arrangements remain in acceptable condition
- The cable is properly supported where required
Best practice: Do not treat the cable gland as a minor accessory. It forms part of the interface between the cable and the Ex equipment and can affect the integrity of the installation.
5. Check for Unauthorized Modifications
One of the more difficult inspection problems is identifying modifications that were made after the original installation.
Examples can include additional cable entries, replacement glands, drilling or machining of enclosures, changes to covers, replacement components, or other modifications that were not part of the original certified configuration.
Best practice: When an installation differs from the original documentation, determine whether the modification is authorized and compatible with the equipment certification before accepting it.
6. Verify Equipment Identification and Ex Marking
Equipment identification should remain clear enough to establish what equipment is installed and what certification applies to it.
Check the equipment nameplate and Ex marking for signs of:
- Damage
- Illegibility
- Missing identification
- Incorrect replacement labels
Where necessary, compare the marking with available equipment documentation and certification records.
Best practice: If the Ex marking or equipment identity cannot be reliably established, do not assume that the equipment remains acceptable based only on its physical appearance.
7. Look for Signs of Overheating
Discoloration, damaged insulation, heat marks, or unusual deterioration can indicate that equipment or connections have experienced abnormal temperatures.
During inspection, look for visible signs around:
- Cable terminations
- Terminal compartments
- Enclosures
- Cable glands
- Electrical connections
Where inspection findings indicate a potential electrical or thermal problem, further investigation may be necessary rather than simply cleaning or replacing the visible component.
Best practice: Treat unexplained heat damage as an indication requiring investigation, not merely as a cosmetic defect.
8. Check Earthing and Bonding Arrangements
Earthing and bonding arrangements should be included in the inspection of applicable Ex installations.
Check the condition and security of relevant connections and look for corrosion, looseness, damage, or other deterioration that could affect the intended arrangement.
The inspection should consider both the equipment and the installation as a complete system.
Best practice: Do not assume that an earth connection is satisfactory simply because a conductor is physically present. Its condition and connection should be verified as part of the inspection process.
9. Check the Installation Environment
The environment surrounding Ex equipment can change over time.
Conditions such as corrosion, dust accumulation, chemical exposure, vibration, moisture, temperature, or mechanical damage can affect equipment condition and installation integrity.
Compare the actual environment with the conditions for which the equipment was selected.
Best practice: Inspect the surrounding installation, not only the equipment itself. A change in environmental conditions can become an equipment suitability issue even when the equipment has not been modified.
10. Review Previous Inspection Findings
Inspection is more effective when previous findings are available for comparison.
Recurring problems can indicate that a component is deteriorating or that the underlying installation condition has not been properly addressed.
Useful records include:
- Previous inspection reports
- Outstanding defects
- Maintenance records
- Equipment replacement records
- Modification records
Best practice: Do not treat every inspection as an isolated event. Use previous findings to identify recurring defects and equipment that require closer attention.
11. Maintenance Should Preserve the Original Protection
Maintenance work on Ex equipment should not unintentionally change the characteristics of the certified equipment.
Before replacing components or carrying out repairs, consider whether the replacement part and maintenance method are appropriate for the equipment and its certification.
This is particularly important when working on components that form part of the explosion protection concept.
Best practice: Use the manufacturer's instructions and applicable certification information when carrying out maintenance that could affect the Ex protection.
12. Do Not Close an Inspection Finding Without Verifying the Cause
A common maintenance mistake is correcting the visible symptom without determining why the problem occurred.
For example, replacing a damaged gland may restore the physical condition of the installation, but if the damage was caused by cable movement, vibration, incorrect installation, or mechanical stress, the underlying problem may remain.
Best practice: Where a defect indicates a recurring or systemic problem, investigate the cause before closing the finding.
Inspection Findings: What Should Trigger Further Review?
Not every observation has the same significance. Some findings may require immediate attention because they could affect the explosion protection of the installation.
Examples include:
- Damaged Ex enclosures
- Incorrect or damaged cable glands
- Unauthorized modifications
- Missing or unreadable Ex identification
- Loose or damaged connections
- Evidence of overheating
- Severe corrosion
- Conditions that differ significantly from the original installation requirements
Where the significance of a defect is uncertain, it should be assessed against the applicable inspection requirements, equipment documentation, certification, and competent technical judgment.
Practical Ex Inspection Checklist
The following checklist can be used as a practical starting point during inspection and maintenance activities:
| Inspection Area | What to Check |
|---|---|
| Ex Protection | Protection concept and equipment identification |
| Enclosure | Damage, corrosion, covers, joints, and fasteners |
| Cable Gland | Condition, security, compatibility, and installation |
| Cable Entry | Sealing, unused entries, and physical condition |
| Ex Marking | Identification and marking remain legible |
| Connections | Visible signs of looseness, damage, or overheating |
| Earthing | Applicable earthing and bonding connections |
| Environment | Corrosion, dust, moisture, vibration, and other conditions |
| Modifications | Changes are authorized and properly documented |
| Previous Findings | Outstanding and recurring defects are addressed |
| Maintenance | Work preserves the intended Ex protection |
| Documentation | Inspection and maintenance records are traceable |
What Inspection Should Tell You
An effective Ex inspection should provide more than a simple statement that equipment is in good condition.
It should provide confidence that the equipment remains suitable for its intended hazardous area and that the installation has not developed conditions that could compromise the protection concept.
This requires looking at the equipment, its installation, its environment, and its maintenance history together.
Important Note
This article provides practical guidance based on IEC 60079-17. It does not reproduce or replace the requirements of the standard.
Inspection and maintenance activities should be carried out in accordance with the applicable edition of IEC 60079-17, equipment certification, manufacturer's documentation, project requirements, and applicable local regulations.
Sources
- IEC 60079-17 — Explosive atmospheres — Part 17: Electrical installations inspection and maintenance
- IEC 60079-0 — Explosive atmospheres — Part 0: Equipment — General requirements
- IECEx — International Electrotechnical Commission System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres
Conclusion
Ex equipment should not be considered safe simply because it is certified and continues to operate. Its protection depends on the condition of the equipment and the installation throughout its service life.
Regular inspection and properly controlled maintenance can help identify physical damage, deteriorating cable entries, unauthorized modifications, environmental problems, and other conditions before they become more serious issues.
The practical objective is simple: verify that the Ex protection remains intact, the installation remains suitable, and maintenance does not compromise the original protection concept.
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