Types of Protection for Hazardous Areas

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Most electrical equipment consists of live or active static parts, and in some cases such as motors, solenoid valves and relays have moving mechanical parts, encased in an enclosure. The electrically live conductors are kept out of touch to prevent electric shock hazards. The detrimental effects of the environment e.g. rain, sprayed water, fine dust and particles are kept out of contact with the conductors, insulation, bearings and the like.

The design of the enclosure of electrical equipment with regard to hazardous area applications is defined by several lower case letter codes, mostly single digits for electrical power equipment but occasionally two digits for very low energy electronic equipment. The most frequently encountered codes are d, e, n, p and i. The lesser used codes are o, m, s and q. The table below gives a brief description of each code:

Ex or EEx Code Meaning of Code
d Flameproof Enclosure
e Increased Safety
i Intrinsic Safety. Two types ia & ib
m Encapsulated Enclosure
n Basically a UK concept that is similar to type ‘e’,
but only for use in Zone 2 areas
o Oil-immersed enclosure
p Pressurization and continuous dilution by
non-hazardous air or inert gas such as nitrogen
q Sand-filled enclosure
s Special designs of enclosure or system of

The codes are usually embraced with double or single quotation marks or less often single round brackets ( ). The code is prefixed with the letters Ex or EEx. Occasionally two letters are combined for special designs of equipment e.g. Ex ‘de’ for some types of motors