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Local Fuel plc - Shoreham Oil Terminal
Safety Instrument System Functional Safety Assessment Stage 5
P & I Design Ltd
DOCUMENT NO: LF364100_RPT
2 Reed Street, Thornaby, UK, TS17 7AF
ISSUE: A DATE: 15.06.2015
Tel: + 44 (0)1642 617444
PAGE 19 OF 32
Fax: + 44 (0)1642 616447
www.pidesign.co.uk5.3 SIL Verification
Document LF364006_RPT Revision A was reviewed as part of this FSA. It was noted that it
has been written for inclusion of the new SIL rated XV162 actuator but not for the later
modification for the change of two gasoline tanks to Marine Oil tanks. Again, depending on
the outcome of Action 1, this document may also need revising, see also Action 7 regarding
the title.
As part of the FSA SIL Verification, the data used to calculate the pfd was reviewed and
detailed below:
Sensor:
The sensors employed within the SIS are Drexelbrook Intellipoint RF transmitters providing
a 4 – 20mA signal, although this is not analog in normal understanding of analog. The devices
utilises this as a carrier signal and depending on the status of the sensor provides a
corresponding mA signal: 8mA - Alarm, 16mA - Normal, 22mA – Fault.
The failure data is provided as:
The calculation within the SIL Verification document Section 6.5 utilises the above data and
confirms that a PFD = 3.38x10
-4
it is noted that the calculation refers to this pfd being for
perfect testing and imperfect testing provides a pfd of 8.57x10
-4
. The device has a SFF of 0.93
and as such satisfies HFT = 0 in accordance with BS EN 61508.
Action 8: