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Safety and environmental standards for fuel storage sites
Final report
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Annex 3
Paraffins
Aromatics
Naphthenes
Composition % (w/w)
C4 C5 C6 C7 C8 C9 C6 C7 C8 C9 C5 C6 C7
Naphtha (worst case)
9 58 20
4
7 2
Naphtha (typical)
2 56 21 6 1
3 1
2 5 3
Raw gasoline (worst)
2 20 20
35 15 8
Raw gasoline (typical)
1 9 21
35 13 7 14
Benzene heartcut
50
50
Reformate (worst)
22 27 3
21 25 2
Reformate (typical)
4 18 17 4 5 24 23 5
Heavy reformate
4 5 3
1 31 34 22
Paraffins
Aromatics
Nap
Composition (w/w)
C2
C3
C4
C5
C6
C7
C6
C7
C5
F3 condensate
0.3 4.4 6.5 4.1 6.5 4.7 1.4 2.8
Anusa
0.02 0.4 1.78 2.72 2.3
1.42
0.28
Brent
0.07 0.74 1.75 2.65 2.27 2.84 2.53 1.25 1.5
Arabian
0.57 0.76 1.75 1.53 1.68 1.22 0.37 0.08
The balance of the crude oil mixture is modelled as a range of low volatility alkanes (not shown).
Part 2 Consideration of substances other than gasoline that may give rise to a
large vapour cloud in the event of a tank overfill
1 Application of the methodology outlined in Part 1 of this appendix indicates that there are a
number of other liquids stored in bulk at COMAH establishments that have a similar potential to
gasoline to generate a flammable vapour cloud in the event of an overfill.
2 There is no simple definition based on a single liquid physical property that could be used
to determine the extent to which other liquids give rise to similar risks to those associated with
gasoline. There are some highly flammable liquids that on the basis of the application of the
methodology clearly would not give rise to a large vapour cloud. These include: methanol, ethanol
and higher chain alcohols, solvent SBP3 and middle distillate oil products such as kerosines and
diesels.
3 However, there are a number of substances where the application of the methodology
indicates that the result of a tank overfill would produce a flammable air mixture near to the lower
flammable limit, or only just above the lower flammable limit under certain release conditions.
4 It is recognised that there is still uncertainty over the behaviour of hydrocarbon releases from
the top of overfilled tanks. This uncertainty cannot be resolved without considerable additional
experimental work. Under the circumstances it is difficult to apply judgement to decide whether a
multiple of lower flammable limit should be used as a criterion for including liquids in scope. One
view is that if the methodology indicates that a vapour mixture above the lower flammable limit
could be produced, then there was not a rational basis for treating these substances differently
to gasoline. However, it is recognised that a judgement on the risk indicated that there was a low
likelihood of the specific release circumstances required to produce a vapour cloud significantly
worse than that arising from a large spill into a bund.