Inspection Grades (Visual, Close, Detailed)

Inspection Grades: Visual, Close, and Detailed

Not all ATEX inspections are equal. EN/IEC 60079-17 defines three distinct grades, each with increasing levels of thoroughness. Understanding these grades helps you apply the right level of scrutiny to different equipment and situations—thorough enough to catch real problems, but practical enough to implement across a large installation.

Visual Inspection

Visual inspection is exactly what it sounds like—identifying defects apparent to the eye without using access tools or equipment. You're looking for obvious problems: physical damage to enclosures, corrosion, missing components, loose fittings, incorrect or illegible labels, signs of unauthorised modification, and evidence of overheating (discolouration, melted components).

Don't dismiss visual inspection as superficial. A trained inspector can spot many critical issues just by looking: a flameproof enclosure with visible corrosion on the flamepath face, a cable gland that's clearly loose, warning labels that have faded to illegibility, or an enclosure that's been opened and not properly re-sealed. Visual inspection forms the foundation for all other grades—if something looks wrong, it almost certainly is.

Close Inspection

Close inspection includes everything in visual inspection, plus checks that require the use of access tools—but critically, without opening enclosures or removing covers. You might use a torch to see into dark areas, a mirror to check behind equipment, or tools to verify that bolts are properly tightened and cable glands are secure.

At this grade, inspectors check that cable entries and glands are correctly fitted and sealed, that all bolts and fixings are present and secure (not just visually, but by feel and torque where accessible), that conduit and trunking connections are tight, that earth continuity bonding appears intact, and that enclosure seals and gaskets show no deterioration.

Close inspection strikes an effective balance between thoroughness and practicality. It catches many significant defects—loose glands, missing bolts, deteriorated seals—without the time and complexity of opening every piece of equipment.

Detailed Inspection

Detailed inspection is the most thorough grade. It includes everything in close inspection plus opening enclosures, removing covers, and using test equipment. This means checking internal component condition, verifying earth continuity with instruments, measuring insulation resistance, examining elements that aren't visible from outside, and—for specific protection types—performing type-specific checks.

For a flameproof enclosure, detailed inspection means measuring flamepath gaps with feeler gauges and checking flamepath surfaces for pitting, corrosion, or damage. For intrinsically safe circuits, it means verifying barrier parameters and earth connections. For increased safety equipment, it includes checking terminal tightness and internal condition. The level of access determines what defects you can find—internal corrosion, damaged components, incorrect wiring, signs of water ingress.

Which Grade for Which Situation?

The required grade depends on the zone classification, the protection type, and whether it's initial or periodic inspection:

• Initial inspection before commissioning typically requires detailed inspection—you need to verify the complete installation before it goes live
• Periodic inspection in Zone 0/1: Generally needs close or detailed inspection at regular intervals, with visual inspection between
• Periodic inspection in Zone 2: May allow visual inspection for routine checks with less frequent close or detailed inspections

EN/IEC 60079-17 provides tables showing recommended grades for different protection types. However, your specific requirements should be based on equipment type, environmental conditions, and operational experience. Your Explosion Protection Document should specify which grade applies to each piece of equipment and how often.

Escalation Principle

An important principle: the specified grade is always a minimum. If a visual inspection reveals something concerning—a suspicious stain, a slightly loose fitting, unexpected vibration—the inspector should escalate to a higher grade for that equipment regardless of what was scheduled. Good inspectors use their judgement, and the standard supports this. Conversely, if a detailed inspection consistently finds no issues with a particular equipment type in a particular environment, you may be able to adjust future inspection intervals—provided this is documented and justified.

Practical Considerations

Detailed inspection requires planning because equipment may need to be isolated and de-energised, which means production impact. Smart inspection programmes schedule detailed inspections during planned shutdowns where possible. They also group equipment by location so inspectors can work efficiently through an area rather than making repeated visits.

Whatever the grade, the inspector must be competent—they must understand both what to look for and why it matters. A visual inspection by someone who doesn't know what a flamepath is, or why a missing earth bond matters, has limited value. Employer responsibilities include ensuring inspection personnel have appropriate training and qualifications.