Ex Basic Principles by Atex Equipment Limited - Explosion Proof and Instrumentation Specialists

Principal applications

Parts which can ignite an explosive atmosphere are placed in an enclosure which will withstand the pressure and prevent the explosion being transmitted to the atmosphere around the enclosure

Additional measures are taken to achieve a higher level of safety, avoiding the risk of impermissibly high temperatures, the occurrence of sparks or arcs internally

Equipment within the hazardous area contains only intrinsically safe (I.S.) circuits. A circuit is I.S. if no sparks or thermal effects occur under established test conditions which could lead to the ignition of an explosive atmosphere

Equipment which could ignite an explosive atmosphere is embedded in a casting compound

Equipment incapable of igniting an explosive atmosphere (in normal and defined abnormal operating conditions)

Equipment immersed in a protective liquid in such a way that an explosive atmosphere above the surface or outside the enclosure cannot be ignited

Equipment is placed in an enclosure with a protective gas overpressure relative to the surrounding atmosphere. If necessary the enclosure is permanentlysupplied with protective gas to dilute flammable mixtures

Equipment is fixed in a position and completely surrounded by finely ground solids to prevent ignition of the surrounding explosive atmosphere


Protection Type to IEC or EN Standards	Basic Principle	Schematic	Principal applications
(d) Flameproof Enclosure IEC 60079-1 EN 50 018	Parts which can ignite an explosive atmosphere are placed in an enclosure which will withstand the pressure and prevent the explosion being transmitted to the atmosphere around the enclosure		Switchgear and switching installations, control and display units, transformers, motors, heating devices, control boards (all types of items producing ignitable arcs in normal operation)
(e) Increased safety IEC 60079-7 EN 50 019	Additional measures are taken to achieve a higher level of safety, avoiding the risk of impermissibly high temperatures, the occurrence of sparks or arcs internally		Terminal and connection boxes, control boxes containing installed components protected by another Ex protection method, squirrel cage motors and light fittings
(i) Intrinsic safety IEC 60079-11 EN 50 020	Equipment within the hazardous area contains only intrinsically safe (I.S.) circuits. A circuit is I.S. if no sparks or thermal effects occur under established test conditions which could lead to the ignition of an explosive atmosphere		Measurement, control and communication equipment, sensors and actuators (low electric values)
(m) Encapsulation IEC 60079-18 EN 50 028	Equipment which could ignite an explosive atmosphere is embedded in a casting compound		Switchgear for low powers, control gear, indicating and display equipment or sensors
(n) Protection IEC 60079-15 EN 50 021	Equipment incapable of igniting an explosive atmosphere (in normal and defined abnormal operating conditions)		All electrical equipment suitable for zone 2
(o) Oil immersion IEC 60079-6 EN 50 015	Equipment immersed in a protective liquid in such a way that an explosive atmosphere above the surface or outside the enclosure cannot be ignited		Transformers (rarely used)
(p) Pressurization IEC 60079-3 EN 50 016	Equipment is placed in an enclosure with a protective gas overpressure relative to the surrounding atmosphere. If necessary the enclosure is permanentlysupplied with protective gas to dilute flammable mixtures		Switching and control cabinets, analysis devices, large motors
(q) Powder Filling IEC 60079-5 EN 50 017	Equipment is fixed in a position and completely surrounded by finely ground solids to prevent ignition of the surrounding explosive atmosphere		Electronic devices