IEC 60079-7 — Ex e Increased Safety Explained

IEC 60079-7 is the part of the IEC 60079 series covering Ex e increased safety equipment. Ex e is one of the most common protection types on industrial sites, used for junction boxes, terminal boxes, luminaires, motors, and control stations in Zone 1 and Zone 2 areas.

The Increased Safety Principle

Unlike Ex d (which contains an explosion), Ex e works by preventing sparking or high temperatures from occurring in the first place. It achieves this through enhanced construction requirements that go beyond standard industrial equipment:

• Minimum creepage and clearance distances — prevents tracking and arcing between live parts
• Minimum IP rating — IP54 minimum for Zone 1 (IP65 for dusty environments)
• Temperature limits — surface temperatures must not exceed T-class limits
• Secure terminal connections — terminals must resist loosening under vibration
• Limited conductor exposure — maximum 1mm of uninsulated conductor beyond terminal

Terminal Requirements — IEC 60079-7

Terminal requirements are strictly defined in IEC 60079-7 and are frequently tested in CompEx Ex01/Ex03:

• Maximum 1mm of bare conductor beyond the terminal ferrule
• Ferrules are mandatory — bare wire in Ex e terminals is not acceptable
• Terminal screws must be locked against vibration loosening
• Cable conductors must be identified and segregated correctly

Cable Gland Requirements for Ex e

Cable gland accessory requirements differ significantly between Ex d and Ex e:

• Ex e threaded entry — non-barrier gland, nylon IP washer required externally to maintain IP rating
• Ex e clearance entry — non-barrier gland, nylon IP washer + serrated washer + locknut externally
• Metal body with continuity plate — internal serrated washer + locknut to maintain armour continuity
• Polyester body, no continuity plate — individual banjo earth tag on every gland + 6mm² links between tags