Inspections

Good inspections are not achieved by walking through an installation with a checklist, but by first understanding what the installation is intended to control. In practice, the difference between a superficial inspection and a proper Ex inspection lies primarily in the preparation. An inspector must not only check whether a cable gland is tight, a stopping plug is present or a nameplate is legible. He must understand why that item of equipment is installed at that location, which hazardous area zone has been classified there, which explosive atmosphere may be expected, which EPL is required, which type of protection has been applied, and whether the actual installation still corresponds with the design, the certificate and the verification dossier.

A good inspection therefore always starts with the documentation. The hazardous area classification, the explosion protection document, equipment registers, certificates, datasheets, installation drawings, cable data, maintenance history and previous inspection reports together form the starting point. Without this basis, an inspection quickly becomes a visual walk-through without sufficient technical depth. In the chemical industry this is especially important, because minor changes in medium, temperature, pressure, ventilation or release source can directly affect the zone classification or the suitability of the equipment. In the food and powder industry, the same applies to dust layers, cleaning regimes, product changes and extraction systems. In wastewater treatment plants and biogas installations, corrosion, H₂S, methane, moisture, ageing and outdoor installation conditions often play a major role. In energy systems, battery charging rooms and utilities, closer attention must be paid to hydrogen formation, ventilation, electrical installations, charging regimes and ignition sources outside the standard production process.

The inspection methodology must be aligned with IEC 60079-17. This means that the required type of inspection must first be determined: an initial inspection before commissioning, a periodic inspection during operation, a sample inspection, or continuous supervision by competent personnel. The appropriate inspection grade is then selected. A visual inspection is suitable for identifying obvious defects such as damage, missing markings, corrosion, dust accumulation, open cable entry holes or incorrectly installed equipment. A close inspection goes further and also assesses items that are visible without dismantling but with the use of tools or access equipment, such as loose connections, cable entries, earthing, seals, fastenings and environmental influences. A detailed inspection is required when the type of protection itself must be assessed in depth, for example with Ex d flamepaths, Ex e terminal compartments, Ex i circuits, Ex p pressurisation systems or Ex t dust protection. In such cases, equipment often has to be opened, measured, checked and compared with the certificate and documentation.

Experience shows that the best results are achieved when the inspection is not carried out component by component, but by installation area or process section. The inspector then does not simply walk past motors, switches and instruments, but follows the process: where can a release occur, how do gas or dust disperse, which items of equipment are installed there, which ignition sources are present, and which technical or organisational measures must control the risk? This makes it much easier to determine whether reality still matches the original assessment. A Zone 2 area that is now structurally contaminated with dust layers may present a different risk profile in practice. An Ex e motor that is suitable on paper may have become unsuitable due to incorrect cable glands, missing strain relief or damaged seals. An Ex d enclosure may be correctly certified, but may lose its protective function due to damaged threads, corrosion in the flamepath or unsuitable sealing compounds. An Ex i circuit may appear safe at first sight, but due to modified cabling, missing segregation or unchecked entity parameters, it may no longer be demonstrably intrinsically safe.

A good inspection therefore always considers three layers at the same time: suitability, installation quality and condition of preservation. Suitability means that the equipment used is appropriate for the zone, gas or dust group, temperature class or maximum surface temperature, EPL, ambient temperature and external influences. Installation quality means that the equipment has been installed in accordance with the relevant installation requirements, using suitable cables, cable glands, seals, earthing, equipotential bonding, mechanical protection, IP protection and segregation of circuits. Condition of preservation means that the equipment has not been degraded by use, contamination, corrosion, vibration, moisture, mechanical damage or maintenance activities. This third layer in particular is underestimated in many companies. An installation may have been correct at handover, but five years later may no longer comply due to maintenance, modifications and operating conditions.

Achieving a good inspection result therefore requires discipline during execution. The inspector must not only record deviations, but also assess their technical significance. A missing nameplate is not merely an administrative deviation; without marking, it can no longer be demonstrated that the equipment is suitable for the zone. A loose cable gland is not merely an installation error; with Ex e it may affect strain relief, IP protection and protection against unwanted ingress. Corrosion on an Ex d enclosure is not merely a maintenance issue; if the flamepath is affected, the flameproof function may be called into question. Dust accumulation on a motor or luminaire is not merely a housekeeping issue; it can cause thermal insulation, increased surface temperatures and a higher ignition risk. The value of a good inspection is therefore not found in the number of observations, but in the quality of the assessment and the prioritisation.

The main differences between industries lie in the focus of the inspection. In the chemical industry, attention is often directed towards gas and vapour zones, process changes, flanges, pumps, sampling points, ventilation, instrumentation and corrosive atmospheres. In that environment, the inspector must have a strong understanding of the relationship between process safety and explosion protection. In food, feed and powder processing, the focus is more often on dust accumulation, cleanability, mechanical ignition sources, filters, elevators, mixers, conveying systems, dust extraction and Ex t equipment. In those environments, inspection must not be limited to electrical equipment; mechanical equipment in accordance with ISO/IEC 80079-36 and 80079-37 must also be considered. In pharmaceuticals and fine chemicals, smaller installations with changing products, temporary set-ups, laboratories, pilot plants and high documentation requirements are often encountered. In these environments, management of change is critical. In wastewater treatment, biogas and waste processing installations, methane, H₂S, moisture, outdoor installation, ageing and limited documentation are often the dominant factors. In storage, transfer and logistics, loading and unloading points, pumping operations, IBCs, tank bunds, battery charging areas, ventilation and electrostatic charging are often decisive. In manufacturing industries, risks often arise from local processes such as spraying, cleaning, degreasing, bonding, printing, wood dust, metal dust or temporary work that was never fully included in the original hazardous area classification.

Ultimately, an inspection must lead to demonstrable control. This means that the report must not end as a long list of isolated comments. It must clearly show which deviations are immediately safety-critical, which deviations affect compliance, which items need to be addressed through maintenance, and which deficiencies relate to documentation or management. The best reports link each finding to the location, installation part, type of protection, normative requirement, risk significance, corrective action and urgency. This allows a company to manage the situation effectively. A technical manager needs to know what must be made safe today, what can be corrected during a shutdown, what must be structurally included in the maintenance plan, and where the explosion protection document or verification dossier must be updated.

In practice, the best result is achieved when inspection is not treated as a one-off control activity, but as part of the explosion protection management system. The initial inspection ensures that the installation is suitable and correctly installed before commissioning. Periodic inspections monitor the condition during operation. Sample inspections help identify trends. Continuous supervision by properly instructed technicians and operators prevents small deviations from remaining unnoticed for years. The inspection programme must therefore be aligned with the risks of the industry, the severity of the zone, the types of protection applied, the environmental conditions, the quality of maintenance and the history of deviations. A clean, dry and stable installation requires a different inspection frequency from a wet, corrosive, dusty or mechanically demanding environment.

A good Ex inspection is therefore not an administrative obligation, but a technical assessment of reality. The central question is always: is the installation, as it is operated today, still suitable for the explosion risk it is intended to control? When this question is answered systematically, the result is what companies need: less uncertainty, fewer hidden defects, better maintenance priorities, a stronger verification dossier and an installation that is defensible during audits, insurance assessments, regulatory inspections and internal safety reviews. That is ultimately the value of a good inspection: not only identifying what is wrong, but making demonstrable what is safe, controlled and recoverable.