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Immingham Storage Co Ltd - East Terminal
Gasoline Storage Tanks Overfill Safety Instrument System - Functional Safety Assessment Stage 2/3
P & I Design Ltd
DOCUMENT NO: SI277016_RPT
2 Reed Street, Thornaby, UK, TS17 7AF
ISSUE: D DATE: 25.04.13
Tel: + 44 (0)1642 617444
PAGE 9 OF 33
Fax: + 44 (0)1642 616447
www.pidesign.co.ukLOPA study Results
Scenario 1
- Overfill of gasoline tank during import from a ship leading to a potential
open vapour cloud explosion causing up to 3 on-site fatalities and up to 6 off-site
fatalities.
Risk Tolerance Criteria
=
1.0 x 10
-6
per year
Frequency of Mitigated Consequence
=
7.58 x 10
-7
per year
The risk tolerance criteria is within the Broadly Acceptable region for up to 10
fatalities (Table 2 - Tolerable Risk Criteria). The frequency of Mitigated Consequence
with a mid-range SIL 2 SIS is well within the “Broadly Acceptable” region.
Scenario 2
- Overfill of gasoline tank during import from a ship leading to a potential
flash fire causing up to 1 on-site fatality and no off-site fatalities.
Risk Tolerance Criteria
=
1.0 x 10
-5
per year
Frequency of Mitigated Consequence
=
8.81 x 10
-7
per year
The risk tolerance criteria is within the Broadly Acceptable region for up to 1 fatality
(Table 2 - Tolerable Risk Criteria). The frequency of Mitigated Consequence with a
mid-range SIL 2 SIS is well within the “Broadly Acceptable” region.
Scenario 3
- Overfill of gasoline tank during import from a ship leading to a potential
open vapour cloud explosion and a release to the River Humber corresponding to a
potential short-term major environmental consequence to the River Humber which
could constitute a threat to the environment. (Consistent with Table 4 - Environmental
Tolerable Risk Frequency).
Risk Tolerance Criteria
=
1.0 x 10
-6
per year
Frequency of Mitigated Consequence
=
6.06 x 10
-7
per year
The risk tolerance criteria is within the Acceptable region for a severe environmental
consequence (Table 4 - Environmental Tolerable Risk Frequency). The frequency of
Mitigated Consequence with a mid-range SIL 2 SIS is well within the “Broadly
Acceptable” region.
The envelope that the LOPA was based on has not changed.
HSE have reviewed the LOPA and accepted the requirement for a SIL 2 protection system.
See letter from HSE regarding COMAH; 3
rd
November 2011.
The operational basis of the LOPA was confirmed at the FSA.