Page 245 - Electrical Installation in Hazardous Area

9

Apparatus using protection

concepts encapsulation ‘m’, oil
immersion ‘0 ’, and powder filling ‘q’

(BS/EN 5001 5 (1 994))

(BS/EN 5001 7 (1 994))

(BS 5501 part 8 (1 998))

This is the first of eight chapters dealing with specific protection concepts
(types of protection). It will deal with three types of protection which are
not yet in common use in the UK, were not developed in the UK, but are
included in the protection concepts covered by Directives 76/117/EEC’ and
94/9/EC.2 Although the use of protection concepts ’0’ and ’q’ is currently
limited to Zone 2 in the UK, it is very likely that they will be permitted
in Zone 1 when the Directive concerned with safety at work eventually
becomes law. They are permitted in Zone 1 in the countries from which
they origmated.

9.1 Encapsulation - ‘m’
BS 5501 part 8 (1 988)3
(EN 50028 (1 987))

The first matter which must be dealt with in this Standard is the fact that
it still exists in its first edition and relates to the first edition of EN 50014
which is BS 5501, Part 1 (1977).4 It does, however, exclude many parts of
that Standard and there is little difference between those that remain and
their equivalents in the second edition, BS/EN 50014 (1993).s

9.1. 1 Exclusions from BS 550 1, Part 1 (1 977)

The parts which are excluded are:

1. Requirements for maximum surface temperature in respect of Ex-m
components.
2. Time delays for opening of enclosures (obvious as it is not possible to
open encapsulation without destroying it).