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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 25 OF 38
Fax: + 44 (0)1642 616447
www.pidesign.co.ukInitiating Event 3
Cause
Description
Notes
No of
events/year
3
ATG Failure
(Sticks or reads
low). This can
happen during
import or tank to
tank transfer.
The allowable failure data for an ATG
(Not SIL rated) is a frequency of not better
than 1e
-5
/hr. Site reliability data suggests a
figure lower than this however this is not
readily verifiable. Manufacturer gives a
MTBF (all modes) of over 50 years for
Motherwell Gauges. Note: See sensitivity
section 5.4
0.1
AND Enabling Event 1 The Tank has to be on fill and the total
proportion of the year when import to the
tank is ongoing during 4:00pm and 8:00
am. Probability = 0.000642. This
explicitly assumes that the ATG has not
failed at the start of import. The ATG is
monitored at the start of import, thus the
ATG not failed is confirmed.
0.00642
Overall Frequency of Initiating Event :
(0.1) x (.000642)
= 6.42 x 10
-5
/year
Based upon 3 night time operations
Note 1:Reliability Data for ATG/BPCS
The LOPA uses an order of magnitude 0.1 PFD for the level and control system. This is the
maximum that can be taken for a non SIS system not designed to BS EN 61511. However,
there is a modern control system designed with a significant amount of diagnostics
utilising modern process control instrumentation.