IEC 60079-17 governs inspection and maintenance of hazardous area electrical installations throughout their service life. This unit covers the four types of inspection, three grades, deficiency categories, inspection intervals, personnel qualifications, documentation, and maintenance requirements.
Learning Objectives
State the four types of inspection defined in IEC 60079-17
Define Visual, Close, and Detailed inspection grades and what each identifies
State periodic inspection interval limits for fixed and portable equipment
Identify deficiency categories X, A, B, C and required actions for each
Describe documentation required before conducting an inspection
State personnel competency requirements and re-assessment intervals
Describe maintenance requirements including replacement parts and repair principles
Four Types of Inspection
Type
Definition
Initial
All equipment before first energisation. Verifies installation appropriate. Grade: as per IEC 60079-17 Tables 1–4.
Periodic
Routine inspection at defined intervals — Visual or Close grade. Frequency by zone, environment, previous results.
Sample
Proportion of equipment to monitor environmental effects and design weaknesses across the population.
Continuous
Frequent attendance by skilled personnel familiar with the specific installation.
Three Inspection Grades
Visual
No tools, normal viewing distance. Missing bolts, rubber bungs, wrong gas group, damaged cables, missing dataplates. Energised equipment acceptable.
Close
Tools and access equipment, no disassembly. Loose bolts, flamepath face sealant/corrosion, cracked gasket, gland pull-test. Generally energised.
Detailed
Opening, disassembly, instruments. Flamepath gap (feeler gauges), terminal torque, tE relay setting verification, IS entity parameters, interlock function. Requires de-energisation.
Deficiency Categories
Category
Description
Action
X — Danger
Immediate danger — could cause ignition
Withdraw from service immediately
A — Potentially Dangerous
Significant risk but not immediately dangerous
Remediate urgently with defined timescale
B — Not Yet Dangerous
Deficiency present but low immediate risk
Schedule at next planned maintenance
C — Observation
Minor point for awareness
Record and monitor
Category X Examples
Rubber bung in Ex d entry; Ex p interlock bypassed; IS wiring unsegregated; Zone 2 equipment in Zone 1; wrong gas group for atmosphere; jointing compound on flamepath.
Inspection Intervals
Fixed equipment: intervals shall not exceed 3 years without seeking expert advice
Movable equipment (portable/hand-held): Close inspection at least every 12 months
Frequently opened enclosures (battery housings etc.): Detailed inspection at least every 6 months
User visual check before each use
Personnel Competency
Operatives must possess: understanding of Ex protection principles and marking; familiarity with specific inspection techniques; understanding of PTW and safe isolation in Ex context; comprehensive understanding of IEC 60079-14 and general understanding of IEC 60079-19.
Competency must be re-assessed at intervals not exceeding 5 years — directly aligning with CompEx 5-year renewal.
Quick Check — 5 Questions
Test key concepts from this unit before moving on.
Q1Summary
Maximum interval between periodic inspections for fixed Ex equipment?
Maximum 3 years for fixed equipment without seeking expert advice. Portable equipment: 12 months. Frequently opened enclosures: 6 months.Ref: IEC 60079-17
Q2Summary
Overload relay tE time verification requires which inspection grade?
Verifying relay setting against tE requires access to the relay, reading the setting, and testing against the motor nameplate IA/IN and tE. Requires opening the MCC or starter panel — Detailed inspection, de-energised.Ref: IEC 60079-17
Q3Summary
Missing dataplate on an Ex junction box — what category?
Category A. Without the dataplate, equipment suitability cannot be confirmed. Seek serial number records to obtain replacement. If suitability cannot be confirmed from any source, escalate to Category X.Ref: IEC 60079-17
Q4Summary
Which inspections can be carried out with equipment energised?
Visual and Close do not require opening equipment and can be performed energised. Detailed inspection — which includes cover removal, gap measurement, and relay testing — requires de-energisation.Ref: IEC 60079-17
Q5Summary
Personnel competency re-assessment interval per IEC 60079-17?
Competency must be re-assessed at intervals not exceeding 5 years. CompEx certification (valid 5 years) directly satisfies this requirement.Ref: IEC 60079-17
EX Academy — independent CompEx-style preparation. Not official CompEx course materials.
Unit 11 · Ex02 & Ex04 · Full Manual
Inspection and Maintenance — IEC 60079-17
IEC 60079-17 governs inspection and maintenance of hazardous area electrical installations throughout their service life. This unit covers the four types of inspection, three grades, deficiency categories, inspection intervals, personnel qualifications, documentation, and maintenance requirements.
Learning Objectives
State the four types of inspection defined in IEC 60079-17
Define Visual, Close, and Detailed inspection grades and what each identifies
State periodic inspection interval limits for fixed and portable equipment
Identify deficiency categories X, A, B, C and required actions for each
Describe documentation required before conducting an inspection
State personnel competency requirements and re-assessment intervals
Describe maintenance requirements including replacement parts and repair principles
11.2 General Requirements
IEC 60079-17 governs inspection and maintenance throughout the service life of hazardous area electrical installations. The explosion protection features designed into Ex equipment must be preserved throughout service life — deterioration of these features can create ignition sources.
Inspection covers three elements:
Verification of the wiring installation up to the point of utilisation (BS 7671)
Inspection of equipment and associated wiring forming the complete installation
Functional check to ensure the system operates as intended
11.3 Safe Electrical Isolation for Inspection
Before any work involving opening Ex equipment in a hazardous area, all incoming and outgoing connections including the neutral conductor must be isolated and locked off. Effective measures must prevent restoration of supply while unprotected live conductors could be exposed to a flammable atmosphere.
IS circuits: formal isolation is not normally required before IS inspection — IS circuits are energy-limited by design. A PTW should still be used, and manufacturer documentation consulted for live work limits.
11.7.1 Four Types of Inspection
Initial Inspection
Carried out on all equipment before first energisation. Verifies the selected types of protection and their installation are appropriate. Results must be recorded. No faults are permissible on handover of a newly installed IS system.
Periodic Inspection
Routine inspection at defined intervals. Visual or Close grade. Intervals determined by manufacturer guidance, zone, previous inspection results, and deterioration factors. Maximum 3 years for fixed equipment; 12 months for portable; 6 months for frequently opened enclosures.
Sample Inspection
Inspection of a representative proportion of equipment and installations. Used to monitor environmental effects, vibration, and inherent design weaknesses across a population without inspecting every item.
Continuous Supervision
Frequent attendance by skilled personnel who are familiar with the specific installation and its environment. May substitute for or supplement periodic inspection.
11.7.2 Inspection Grades
Grade
Method
Examples of What is Found
Power State
Visual
No tools; normal viewing; from ground or platforms
Missing bolts, rubber bungs, wrong gas group, missing dataplate, Ex n in Zone 1
May be energised
Close
Tools and access; physical contact; no disassembly
Flamepath gap (feeler gauge), terminal torque, tE relay, IS entity parameters, IS earth resistance, interlock test
Must be de-energised
Deficiency Categories
Category
Description
Required Action
Examples
X — Danger
Immediate danger
Withdraw from service immediately
Rubber bung in Ex d; bypassed Ex p interlock; wrong gas group; IS wiring unsegregated; jointing compound on flamepath
A — Potentially Dangerous
Not yet dangerous but significant risk
Remediate urgently — defined timescale
Cracked IP gasket; tE relay set too slow; terminal overloaded; missing dataplate
B — Not Yet Dangerous
Deficiency present; low immediate risk
Schedule at next planned maintenance
Minor surface corrosion; slightly loose but held gland; missing paint on body
C — Observation
Minor point for awareness
Record and monitor
Minor finish damage; legibility reduced but still readable; non-safety-affecting deviation
11.10 Maintenance Requirements
Maintain integrity of the type of protection at all times
Replacement parts must comply with the equipment safety documentation — no unauthorised substitutes
Repairs and reclamation must follow IEC 60079-19
Do not interfere with manufacturer anti-static measures
Replacement lamps: correct type and wattage only — wrong lamps raise temperature above T-class
Periodic lamp replacement in Ex e luminaires before end of life — a failing lamp affects T-class compliance
Damaged gaskets: replace with manufacturer-approved type only
Flexible cables: inspect regularly; replace if damaged or defective
Equipment permanently withdrawn: isolate from supply; remove wiring or correctly terminate in appropriate enclosure
Unit 11 Knowledge Check — 10 Questions
CompEx-style questions covering the full unit content.
Q1Unit {num}
What must happen before a new Ex installation is energised for the first time?
Initial inspection must be carried out before first energisation. The grade and items checked are specified in IEC 60079-17 Tables 1–4. For IS systems, no faults are permissible at handover.Ref: IEC 60079-17
Q2Unit {num}
Personnel competency must be re-assessed at what maximum interval?
Competency re-assessment: not exceeding 5 years. CompEx certification valid for 5 years directly satisfies this.Ref: IEC 60079-17
Q3Unit {num}
Minimum periodic inspection interval for portable hazardous area equipment?
Portable/hand-held equipment: Close inspection at least every 12 months. Fixed equipment: maximum 3 years. Frequently opened enclosures: 6 months.Ref: IEC 60079-17
Q4Unit {num}
Original Ex d cover bolts are replaced with standard galvanised Grade 4.6 bolts. Acceptable?
Bolts on which protection depends must match manufacturer specification in grade, material, and dimensions. Non-identical substitutes require authorisation and may affect flamepath clamping force.Ref: IEC 60079-17
Q5Unit {num}
A Close inspection finds severe pitting corrosion on an Ex d flanged joint face. What category and next step?
Corrosion pitting may have widened the flamepath gap beyond permitted limits. Close inspection identifies the corrosion but cannot measure the gap. Escalate to Detailed — measure gap with calibrated feeler gauges. Return to service only if within IEC 60079-1 Table 1 or 2 tolerance.Ref: IEC 60079-17
Q6Unit {num}
Can IS circuit inspection be carried out without formal electrical isolation?
IS circuits are designed to be below ignition energy under fault conditions. Formal electrical isolation is not normally required. PTW controls the work; specific live-work limits are defined in the IS system documentation.Ref: IEC 60079-17
Q7Unit {num}
What must happen when Ex equipment is permanently withdrawn from service with cabling left in place?
Permanently withdrawn equipment: isolate from all supply; remove the wiring or correctly terminate in an appropriate enclosure with terminations made safe. Bare cable tails in a hazardous area are an uninspected hazard.Ref: IEC 60079-17
Q8Unit {num}
Which document governs repair and reclamation of Ex equipment after maintenance damage?
Repairs and reclamation must be carried out in accordance with IEC 60079-19 — which covers the procedures, authorisations, and quality controls required for repairing and overhauling Ex equipment without invalidating certification.Ref: IEC 60079-17
Q9Unit {num}
A Zone 2 motor is found running very hot with blocked cooling fan vents. What category?
Blocked cooling fan intake can cause the motor surface to exceed its T-class rating — creating an ignition source. Category A: de-energise, restore cooling, verify surface temperatures return to within T-class limits before return to service.Ref: IEC 60079-17
Q10Unit {num}
Inspection of an Ex e luminaire shows the installed lamp is 2W above the certified maximum wattage. What category?
The lamp wattage forms part of the T-class certification of an Ex e luminaire — the enclosure temperature limit is calculated for the certified maximum wattage. A higher wattage lamp raises temperature above the T-class, creating a potential ignition source. Category A.Ref: IEC 60079-17