Periodic Maintenance and Inspection of Ex Equipment

In the other articles in this Knowledge Center series we have mostly covered the ATEX certification process for a new product. But purchasing and installing Ex-certified equipment is only the first half of the job; ensuring that equipment actually maintains the protection stated on its certificate throughout its service life is a separate, ongoing process that is the operator's responsibility. In this article we cover how periodic maintenance and inspection of Ex equipment is carried out.

Why Is Periodic Inspection Necessary?

A piece of Ex equipment provides a certain level of protection as certified by the manufacturer at the moment of certification; but over time, vibration, corrosion, temperature cycling, faulty maintenance interventions, or gasket/cable entry wear can degrade this protection. For example, wear on the flange gap of a flameproof (Ex d) enclosure, or an unauthorized modification to an intrinsically safe (Ex ia) circuit, can effectively invalidate the protection stated on the equipment's label. Periodic inspection is a systematic safety mechanism that ensures such degradation is detected and corrected early.

Inspection Levels: Visual, Close and Detailed

The EN 60079-17 standard defines Ex equipment inspections at three levels. Visual inspection is a quick observation made from the outside without disassembling the equipment; elements such as label legibility, visible damage to the enclosure, or excessive contamination are checked. Close inspection is a more detailed examination carried out with additional tools but generally without de-energizing; elements such as connection tightness and gasket condition are assessed. Detailed inspection is the most comprehensive level, where the equipment is de-energized and sometimes disassembled to examine internal components when necessary.

How Is the Inspection Interval Determined?

EN 60079-17 does not impose a fixed interval; the interval is determined based on the business's own risk assessment. In general, higher-risk areas such as Zone 0/20 warrant more frequent inspection, while lower-risk areas such as Zone 2/22 can have relatively less frequent inspection. Environmental conditions are also decisive: in environments with high vibration, humidity or corrosive conditions, equipment can wear faster, so inspection frequency should be increased. We covered how zone classification determines risk level in our article What Are Zones 0, 1 and 2?.

Who Can Carry Out the Inspection?

Inspection and maintenance of Ex equipment must be carried out by personnel who have received special training in the relevant protection types and whose competence is documented, beyond general electrical/mechanical maintenance skills. For example, an untrained person closing an Ex d enclosure with the wrong torque value, or replacing a gasket with an uncertified one, can effectively invalidate the protection stated on the equipment's label; this brings both legal liability and genuine explosion risk.

Points to Watch Regarding Spare Parts and Repair

Every component used in Ex equipment (gasket, cable gland, terminal) is an integral part of the certification process. Using a non-original or uncertified spare part, even as a seemingly minor intervention, can affect the equipment's protection performance in an unknown way and effectively invalidate the certificate. For this reason, maintenance and repairs must always use original parts approved by the manufacturer, and the intervention must be carried out in accordance with the manufacturer's instructions.

The Importance of Inspection Records

The result of every inspection (findings identified, corrections made, spare parts used) should be recorded in writing and kept accessible until the next inspection, ideally throughout the equipment's service life. These records serve as critical evidence of the business's due diligence, both in occupational health and safety audits and in any accident investigation. It is recommended that these records be consistent with the facility's overall Explosion Protection Document and reviewed regularly.

How to Set Up a Periodic Inspection and Maintenance Program

• Compile an inventory of all Ex equipment at your facility (category, protection type, installation date, location).
• Determine an inspection interval for each piece of equipment based on the risk level of the zone it is located in.
• Confirm that the personnel carrying out inspections have competence under EN 60079-17.
• Schedule visual, close and detailed inspection levels according to the calendar.
• Record the result of every inspection in a standard format.
• Prioritize identified non-conformities and create a corrective action plan.
• Review the inspection program at least once a year and confirm consistency with the Explosion Protection Document.

Relevant Directives and Standards

The legal basis of the periodic maintenance and inspection obligation is Workplace Directive 1999/92/EC (ATEX 137), which addresses the employer's side; the Explosion Protection Document prepared under this directive requires proving that the protective measures taken are being maintained. The technical methodology of inspection is defined in EN 60079-17 (inspection and maintenance of electrical installations) and, for mechanical equipment, EN 60079-19 (repair, overhaul and reclamation). Competence requirements for personnel carrying out inspections are also within the scope of these standards.

Step-by-Step Process

1. Compile an inventory of the Ex equipment at your facility and determine each item's protection type/category.
2. Determine the inspection interval for each piece of equipment based on the risk level of its zone.
3. Set up the inspection program with competent personnel under EN 60079-17 or an external service provider.
4. Carry out the initial inspection right after installation, before the equipment is put into service.
5. Carry out periodic inspections according to schedule and record the results.
6. Take any equipment with identified non-conformities out of service until corrected.
7. Review inspection records together with the Explosion Protection Document on a regular basis.

Most Common Mistakes

• Servicing Ex equipment the same way as general electrical maintenance, with untrained personnel.
• Using non-original or uncertified spare parts.
• Determining the inspection interval arbitrarily rather than based on risk level.
• Leaving inspection results as verbal notes instead of recording them in writing.
• Continuing to use equipment despite a serious non-conformity being identified.
• Running the inspection program disconnected from the Explosion Protection Document.

Frequently Asked Questions

Conclusion

Certification of a piece of Ex equipment is only the starting point of safety; maintaining that protection throughout the equipment's service life requires a systematic periodic inspection and maintenance program. An inspection program compliant with EN 60079-17, carried out by competent personnel and regularly recorded, both ensures legal compliance and minimizes real explosion risk in the field.