Ex Motors — Selection Inspection and Maintenance Guide
Ex motors are found throughout offshore platforms, petrochemical plants, and industrial facilities — powering pumps, compressors, fans, conveyors, and agitators in hazardous areas. Most process plant Ex motors are Ex d (flameproof) or Ex de (flameproof terminal box with increased safety motor body). Understanding Ex motor inspection and selection is a core CompEx requirement.
Ex Motor Protection Types
| Marking | Description | Zone |
|---|---|---|
| Ex d IIB T4 Gb | Flameproof — entire motor is Ex d | Zone 1 |
| Ex de IIB T4 Gb | Motor body Ex e, terminal box Ex d | Zone 1 |
| Ex e IIB T3 Gb | Fully increased safety motor | Zone 1 |
| Ex ec IIB T3 Gc | Energy-limited motor | Zone 2 only |
Ex Motor Inspection — Key Points
Terminal Box (Ex d)
- All bolts present — count every bolt position (Category X if any missing)
- Cable gland thread engagement — minimum 5 full turns
- Barrier gland fitted if enclosure >2L or clearance entry
- Flamepath condition — clean, undamaged, gap within IEC 60079-1 limits
- All cable entries sealed — glands or stopping plugs
Motor Body (Ex e where applicable)
- Nameplate present and legible — verify EPL, gas group, T-class matches area
- Earth terminal present and connected — external earth tag uncorroded
- Ventilation — cooling fins unobstructed, grilles undamaged
- No physical damage to motor body
EX Academy's Inspection Simulation 01 (PM-101-A) is an Ex d motor in Zone 1 IIB T4. It's the recommended first simulation because it covers the most common inspection scenario on process plant. The deficiencies include missing bolts (Category X), non-barrier gland on a >2L enclosure (Category A), paint on flamepath (Category A), and corroded earth tag (Category B).
Cable Gland Selection for Ex Motors
For Ex d motor terminal boxes, apply the standard Ex d gland selection rules: identify entry type (threaded or clearance), check terminal box volume from the nameplate or certificate, and select barrier or non-barrier accordingly. Most Ex d motor terminal boxes have volumes between 1 and 5 litres — check each one individually.
Interactive inspection simulations, equipment selection decisions, and 1,185+ practice questions referenced to IEC 60079. Try free — no card required.
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