Page 63 - Electrical Installation in Hazardous Area

Area classification 39

containment and the methods of its loading and discharging. In addition,
the physical structures involved must be considered. While, for example, a
solid wall may be an effective barrier to the transmission of an explosive
atmosphere, any door which it contains will have to be considered as a
source of hazard as it communicates with the area on the other side of such
a wall. This is particularly important when considering boundary walls as
it is not generally acceptable to communicate an explosive atmosphere on
to neighbouring sites and any accident which relates to such an activity is
likely to be seen as the responsibility of the creator of the explosive atmo-
sphere. Figures 2.5 and 2.6 show the area classification procedure described
here in tabular form.

2.8 Personnel involved

The area classification procedure can have a significant effect on the design
of a particular process, notwithstanding the effect which its results have on
the acceptability of the process. Its importance cannot be overrated and it
must form one of the prime parts of the design process. This is not only true
from a safety point of view but corrections to a process after design and
construction are complete can be very expensive and can even challenge
the viability of a particular activity resulting in waste of investment. For
this reason, it is necessary that area classification be seen by those involved
as fundamental to the design process and the seniority of those involved
should reflect this. To this end, the area classification procedure should start
as soon as possible after the inception of the design process and be carried
out by a group formally constituted as follows.
The Project manager/zuorks manager; the presence of whom on the area
classification team gives the necessary seniority to ensure the credibility of
the exercise. The project engineer or works manager should chair the group
and, while it is recognized that these senior people may delegate the duty of
area classification, it is stressed that the seniority of the person to whom the
duty is delegated must be sufficient to ensure the credibility of the exercise
and he or she must be seen as the representative of the project engineer or
works manager.
The Process engineer; usually a chemical engineer, is an important part of
the group as he or she will be expert on the performance of the process
materials and their chemical properties. It may be that their involvement is
primarily in the early part of the exercise but he or she should be available
throughout.
The MechanicaZ/machines engineer; is necessary to discussions on the
mechanical properties of the containment and the practicability of any
necessary or advisable modifications. He or she will, or via associates,
also have access to the detail of any special process machinery intended
to be used in the process. The importance of the mechanical aspects of
containment cannot be overstressed.
The Safety Oficer; to advise on the wider aspects of safety so that, for
example, a release acceptable for area classification purposes but not on