Page 27 - Electrical Installation in Hazardous Area

6 Electrical installations in hazardous areas

and more predictable in quantity and frequency, and second the recogni-
tion that far from dealing with one gas and one dust, as in mining, surface
industry was dealing with a myriad of different materials each with its
own characteristics. This recognition led to development of the technique
of area classification to define the risks of explosive atmospheres occurring
in specific locations and the development of additional types of protection
to more readily reflect the varying levels of hazard which could be iden-
tified. It is these two factors that led to the current UK and international
industrial practice which this book seeks to describe.

1.4 UK legislation

The basic historic UK legislation covering the use of electrical equipment
in explosive atmospheres is that included in the Electricity Regulations' of
the Factories Acts3. Regulation 27 of these regulations states:
All conductors and apparatus exposed to the weather, wet, corrosion,
inflammable surroundings or explosive atmosphere, or used in any
process or for any special purpose other than for lighting or power,
shall be so constructed or protected, and such special precautions shall
be taken as may be necessary adequately to prevent danger in view
of such exposure or use.

This regulation clearly states the objective to be achieved but does not define
the method of its achievement. While one may be concerned at this, its intent
is to allow the widest possible range of approaches to the achievement of
the required level of security and thus to give the maximum freedom of
operation to industry, while at the same time, laying upon that industry
the requirement to achieve an adequate level of security in its operation.
Regulation 27 remained in force, even after the enactment of the Health
and Safety at Work Act 1974*, until replaced by Regulation 6 of the 1989
Electricity at Work Regulations5. Regulation 6 states:

Electrical equipment which may reasonably foreseeably be exposed to:-
(a) mechanical damage;
@) the effects of weather, natural hazards, temperature or pressure;
(c) the effects of wet, dirty, dusty or corrosive conditions; or
(d) any flammable or explosive substance, including dusts, vapours
or gases,

shall be of such construction or as necessary protected as to prevent,
so far as is reasonably practible, danger arising from such exposure.

The tenor of this new regulation, now current, is very much the same as its
predecessor. The objective to be achieved is specified and within that objec-
tive maximum freedom is given to industry in methods of its achievement.