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Simon Storage Ltd – Immingham East Terminal
Gasoline Import – Layers of Protection Analysis
P & I Design Ltd
DOCUMENT NO: SI057001_RPT
2 Reed Street, Thornaby, UK, TS17 7AF
ISSUE: G DATE: 29.06.12
Tel: + 44 (0)1642 617444
PAGE 9 OF 34
Fax: + 44 (0)1642 616447
www.pidesign.co.uk3.2
LOPA Model
The following figure shows the principle of the Layer of Protection technique. It is essential
that each layer is independent from each other to ensure that protection is achieved.
Intiating Event
Independent
Protection Layer 1
Independent
Protection Layer 2
Independent
Protection Layer 3
Independent
Protection Layer 4
Outcome
Successfully Operated
Initiating Event
Successfully Operated
Frequency
1
=
x
Failed to Operate
Successfully Operated
PFD
1
= y
1
1
=
x
x
y
1
Failed to Operate
Successfully Operated
PFD
2
= y
2
2
=
x
x
y
1
x
y
2
Failed to Operate
PFD
3
= y
3
3
=
x
x
y
1
x
y
2
x
y
3
Failed to Operate
PFD
4
= y
4
Failure - Incident
4
=
x
x
y
1
x
y
2
x
y
3
x
y
4
Safe
Safe
Safe
Safe
3.3
Calculations
The following calculations are used within this LOPA study:
Frequency of Mitigated Consequence =
CM x{(IEF1 x PL1 x PL2 x PL3 x etc)+(IEF2 x PL1 x PL2 x PL3 x etc )+ (etc)}
Where CM = Conditional Modifiers i.e CM1 x CM2 x CM3 x CM4
IEF = Initiating Event Frequency
PL = Protection Layer