Performing a defensible Ex-Proof / ATEX & IECEx Hazardous Area Electrical Inspection inspection requires more than writing down a number from a display. Auditors, insurers, and national regulatory bodies under IEC 60079-14 / IEC 60079-17 require calibrated instrument traceability, correct lead placement, environmental / temperature compensation, and verification under representative operating conditions.
1. Required Calibrated Test Instruments
Before going to site, register your instrument's brand, model, serial number, and valid calibration expiry date inside OhmCert's Equipment Register. For Module #26 (Ex-Proof / ATEX (IEC 60079)), use:
- Primary Instrument Set: ATEX-Certified Intrinsically Safe Multimeter / Insulation Tester, Calibrated Feelers (Ex d Flamepath Gap Check), Torque Wrench, and Loop RLC Meter (for De-Energized Ex i Entity Verification)
- Traceability Requirement: Valid ISO/IEC 17025 calibration certificate (within 12 months).
2. Step-by-Step Field Connection & Measurement Procedure
- Obtain the Hazardous Area Classification drawing (IEC 60079-10-1 Gas Zones 0/1/2, IEC 60079-10-2 Dust Zones 20/21/22), Substance Group (IIA, IIB, IIC or IIIA, IIIB, IIIC), and Auto-Ignition Temperature T_ait [degC].
- Inspect the Ex equipment nameplate marking and enter Zone, Equipment Protection Level (EPL Ga/Gb/Gc or Da/Db/Dc), Apparatus Group, Temperature Class (T1-T6), and max surface temperature into OhmCert.
- For Intrinsically Safe (Ex ia / Ex ib) loops: verify Zener barrier / galvanic isolator entity parameters U_o <= U_i, I_o <= I_i, P_o <= P_i and confirm total cable capacitance C_c + C_i <= C_o.
- For Ex d flameproof enclosures and Ex e motors: verify all bolts, stopper boxes/barrier glands, non-painted flamepath gaps, PE/equipotential bonding (<= 0.2 Ohm), and Ex e motor t_E trip time (>= 5 s).
3. Governing Equations Evaluated During the Test
As you enter your field readings into OhmCert Module #26 (Ex-Proof / ATEX (IEC 60079)), the engine evaluates these normative formulas in real time:
T_surface_max: T_class_max <= T_AIT (Gas) | T_surface <= (2/3) x T_cloud (Dust) — Maximum equipment surface temperature must not exceed the auto-ignition temperature of the explosive atmosphere (IEC 60079-14 §5.6).
Ex_i Loop: Uo <= Ui, Io <= Ii, Po <= Pi, (Ci + C_cable) <= Co, (Li + L_cable) <= Lo — Intrinsic Safety (Ex ia / Ex ib) entity parameter verification between safety barrier and field instrument (IEC 60079-14 §16.2).
4. The 3 Most Common Field Measurement Mistakes
- Installing an Industrial or Standard IP66 gland (or an unsealed Ex e gland where IEC 60079-14 §10.6.2 requires an Ex d barrier gland) on a Zone 1 flameproof enclosure.
- Installing IIB-marked apparatus in a Hydrogen / Acetylene (Group IIC) zone, or T3 (200 degC) apparatus in a Carbon Disulphide (T_ait = 95 degC -> requires T6 85 degC) atmosphere.
- Painting or greasing Ex d flanged flamepaths with silicone sealant that hardens or blocks flame quenching.
5. Mandatory Site Verification Checklist (22 Normative Points)
- Explosion Protection Document (EPD) and Hazardous Area Classification drawing (Zone 0/1/2, 20/21/22) available and current [IEC 60079-10]
- ATEX / IECEx certificate numbers on equipment nameplates match the hazardous area equipment register [IEC 60079-17 Table 1 A1]
- Equipment Protection Level (EPL Ga/Gb/Gc or Da/Db/Dc) and Ex protection concept match the classified Zone
- Equipment Gas/Dust Group (IIA/IIB/IIC or IIIA/IIIB/IIIC) and Temperature Class (T1-T6) verified for all present substances
- Special conditions of safe use ('X' suffix on certificate) verified and implemented on site
- Ambient temperature range on nameplate (default -20 degC to +40 degC unless marked) suitable for local environment
- Ex d flameproof enclosure flange gaps free of corrosion, paint, non-setting grease alterations, or unauthorized gaskets [IEC 60079-14 §10]
- All Ex d enclosure cover bolts present, of correct property class (e.g. A2-70 / 8.8), and tightened to OEM torque