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Local Fuel – Shoreham Oil Terminal
Gasoline Ship Import – Layers of Protection Analysis
P & I Design Ltd
DOCUMENT NO: LF364002_RPT
2 Reed Street, Thornaby, UK, TS17 7AF
ISSUE: E DATE: 30.07.15
Tel: + 44 (0)1642 617444
PAGE 34 OF 38
Fax: + 44 (0)1642 616447
www.pidesign.co.uk5.3.7 Conditional Modifiers - Scenario 3, Overfill of gasoline tank during import from a ship
leading to an explosion, fire and a release to the Harbour or underground aquifer
corresponding to a potential short-term Major Environmental Consequence.
The probability of the weather conditions being conducive to allow a build-up of vapour
such as to cause an open flammable cloud explosion is extremely low. The figure
considered in this LOPA assumed that the weather conditions had to be E & F conditions
(Stable). (Local Weather data 2009 to 2010, indicates calm conditions for 2% of the time.
Assumed conservative probability = 0.03)
Probability
0.03
2. Probability of ignition
The vapour/mist cloud will be large and may drift. There may be sources of ignition
outside the bund. The site is predominantly flat.
The main site substation is to the east of the gasoline storage bund and would thus be the
main source of ignition. This could limit the extent of the cloud significantly although it
cannot be considered a continuous source of ignition. Possible sources of ignition are
identified in Appendix 8 and the probabilities of an ignition from these sources have been
considered. The site is confined by Large 15m high bank to the north. The probability of a
delayed ignition leading to an explosion was discussed in detail and it was felt that on the
terminal it should not be assumed to be unity. However, offsite sources of ignition are
uncontrollable and thus the overall probability of ignition will be taken as unity. There are
no continuous sources of ignition.
Probability
1.0
3. Probability of bund failure
The probability of gasoline liquid and other components escaping from the bunds in the
event of a fire is dependent on the period of the fire. The tanks are all installed in
impervious bunds with adequate capacity, wall strength, and fire-resistance, but it is
acknowledged that a long period fire may cause some sections of the walls and joints to
become compromised.
Reference “Bund effectiveness in preventing escalation of tanks farm fires”, Davies, Harding, MaKay,
Robinson and Wilkinson, IChemE symposium series No 139. Also published as Process safety and
environmental protection, Trans IchemE vol. 74, n
o
2, pp. 88-93, 1996
Probability of bund wall failure with fire/explosion is taken as
0.8
4. Probability of release into the Harbour
Liquid gasoline and fire-fighting components would need to travel south to reach the
harbour and be of a sufficient quantity and duration to constitute a Major Environmental
Consequence. The bund capacity at terminal is large, in excess of 200% of largest storage
tank. This is seen to be a low probability, however it is unquantifiable and thus no credit
has been taken. This is a very conservative value.
Probability of a release reaching the river is taken as
1.0