Page 105 - Electrical Installation in Hazardous Area

Area classification for gases, vapours and mists 81

sampling point would be within the hazardous area at the time when
flammable materials were present. As the majority of flammable mate-
rials are also toxic this is not a situation which can be accepted. Sampling
arrangements are usually carefully designed to minimize the hazardous
area created in normal operation so that the only significant hazardous
area occurs in abnormal operation.

Sampling liquids

Any sampling point used for sampling liquids should be so arranged that
any spillages occurring during normal sampling are removed immediately.
To do this the sampling arrangements should incorporate features which
satisfy those achieved by the sampling system shown in Fig. 3.15. The
tundish or receptor of spillages below the sampling point should transfer
any spillage to a closed storage facility safe disposal system. For liquids
of low volatility (it is suggested that these will have atmospheric boiling
points of at least four times ambient temperature) the effects of gravity will
normally be all that is needed to ensure spillage collection in the tundish,
but in other cases it is likely that some form of extract system to draw

a=lm

Ground
e SamDle

a=lm
b = p00l
c = Tdbk '3

Fig. 3.15 Liquid sampling