Type of protection “o” Oil immersed

EMMUA 214 States:

Page 24

3.8.1 Definition

Protection is provided by immersing the equipment in oil to a sufficient depth, such that any ignition capable products do not reach the surface where they could ignite any potentially explosive atmosphere. However, precautions are required to ensure an adequate oil level is maintained.

3.8.2 Standards and selection

i) Current standards

IEC 60079-6 (EN 60079-6) Explosive atmospheres - Part 6: Equipment protected by oil immersion.

ii) Superseded standards

EN 50015 Oil immersion Type ‘o’;

BS 5501 Part 2 Oil immersion Type

iii) EPL/category and zones of use

Oil immersion equipment may be used in areas requiring EPL I Gb l and ‘GCT , or Category 2 and 3. Prior to 2007, such equipment was permitted to be used in Zones 1 or 2.

Protection by which parts of the electrical apparatus are immersed in oil such that an explosive atmosphere, which may be above or outside the enclosure, cannot be ignited.

In Europe, oil immersion is suitable for Zone 1 and Zone 2 applications.

Oil immersion has been used for heavy current apparatus, such as transformers and isolating switchgear.

In those applications oil is used to quench (cool) the spark or arc when a transformer fault occurs or an isolating switch is “thrown” closed or open. Sparking in mineral insulating oil does affect the oil composition.

Oil breakdown occurs producing carbon deposits from arcing and, gases such as hydrogen and acetylene are produced.

Those gases are highly flammable.