Abstract
The minimum surface potentials reported for the ignition of hydrocarbon
vapours by discharges from liquid surfaces range from 25 to about
60 KV. In evaluating electrostatic ignition hazards, a suitable threshold
value must be chosen from this range. In this paper the available
results are reviewed and reasons for the spread of values suggested.
It is demonstrated that the relevant threshold for the evaluation
of electrostatic ignition hazards in road- or rail-tanker loading
is about 60 kV. The lower thresholds arise from features of small-scale
laboratory tests that do not occur in full-scale commercial tanker
compartments. The threshold conditions for ignition are often expressed
in terms of the charge transferred by the largest discharges that
can occur. These results are also examined and it is shown that a
threshold of about 80 nC is relevant to full-scale systems. Higher
thresholds (up to 250 nC) may be found in smaller scale systems.
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