The basics of explosion protection - STAHL - #21

Type of protection in accordance with IEC, EN, UL, FM und NFPA

Representation (diagram)

Basic principle

Main application

Oil immersion "o"

EN 60079-6 UL 60079-6

IEC 60079-6 FM 3600

Electrical apparatus or parts of electrical apparatus are immersed in a protective fluid (such as oil), such that a potentially explosive atmosphere existing over the surface or outside of the apparatus cannot be ignited.

Transformers, starting resistors

Powder filling "q"

EN 60079-5 UL 60079-5

IEC 60079-5 FM 3600

Filling the casing of an electrical apparatus with a fine granular packing material has the effect of making it impossible for an electric arc created in the casing under certain operating conditions to ignite a potentially explosive atmosphere surrounding the casing. Ignition must not result either from flames or from raised temperature on the surface of the casing.

Sensors, display units, electronic ballast, transmitter

Encapsulation "m"

EN 60079-18 UL 60079-18

IEC 60079-18 FM 3600

Parts that are capable of igniting an explosive atmo­sphere by either sparking or heating are enclosed in a compound in such a way as to avoid ignition of an explosive atmosphere.

Switchgear with small breaking capacity, control and signalling units, display units, sensors

ma = use in Zone 0, 1, 2 mb = use in Zone 1, 2

Type of protection "n_" EN 60079-15 UL 60079-15

IEC 60079-15 FM 3600

Ii rl

Electrical apparatus cannot ignite a explosive atmosphere surrounding them (in normal operation and under defined abnormal operating conditions).

All electrical equipment for Zone 2

nA = non-sparking apparatus

nC = sparking apparatus in which contacts

are protected conveniently

nL = energy-limited apparatus

nR = purged/pressurized apparatus

nZ = purged pressurized apparatus, n

Optical radiation "op^_" EN 60079-28 IEC 60079-28

Appropriate measures prevent ignition of an explosive atmosphere by optical radiation.

Optical fibre

There are three different methods: Ex op is = intrinsically safe optical radiation Ex op pr = protected optical radiation Ex op sh = blocking optical radiation