Ex Junction Boxes — Selection and Inspection Guide
Ex junction boxes are used throughout hazardous area cable systems to distribute circuits, provide termination points, and enable isolation. They are manufactured as Ex d (flameproof), Ex e (increased safety), or Ex de (combined), and selecting and inspecting the correct type requires a thorough understanding of IEC 60079 requirements.
Ex d Junction Box Selection
For Ex d junction boxes, the critical selection parameters are:
- Zone — most process plant junction boxes are Zone 1 (EPL Gb)
- Gas group — IIA, IIB, or IIC depending on area classification
- Temperature class — must not exceed gas AIT
- Internal volume — determines barrier/non-barrier gland requirement
- Number and size of entries — must accommodate all required cables
Ex d Junction Box Inspection
- All cover bolts present, correct grade, and fully engaged
- Cable gland type correct for volume (barrier >2L, non-barrier ≤2L for threaded entries)
- Minimum 5 full thread turns on all glands and stopping plugs
- Flamepath condition — no paint, corrosion, damage
- All unused entries sealed with certified stopping plugs
- Internal earth link present and connected
- Certificate matches area classification
Selection Scenario 01 (Ex d junction box, 2.5L, Zone 1 IIB) and Scenario 14 (Ex de junction box, Zone 1 IIB) are directly relevant to junction box selection practice. Both require identifying the correct gland type, stopping plugs, accessories, and earthing arrangements.
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