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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 11 OF 33
Fax: + 44 (0)1642 616447
www.pidesign.co.ukATG Alarms via VTW System
Topping Off Alert (Facility available, % to be set 60 minutes from predicted finish time)
Normal Fill Level Alert (Set at 95% at present)
High Level Alarm (Set at 96% at present)
The normal fill level alert and high alarms are purely audible alarms within the control room
and transmitted through the radio system.
It was confirmed:
The TOA is set at 60 minutes from predicted finish time.
Normal Fill Level Alert (Set at 95%).
High Level Alarm (Set at 96%).
There is an independent high high level switch and shutdown system which closes the
Automated Shutdown valve on the receiving tank inlet. The activation of the switch is
transmitted to a control room annunciator and repeated to the radio system. (Set at 97% at
present)
It was confirmed that the high high level switch activation point is 97%
(For tank 561 = 6931mm, time to overfill after high high level activated: 5.4 minutes)
(For tank 564 = 8682mm, time to overfill after high high level activated: 9.9 minutes)
(For tank 568 = 8662mm, time to overfill after high high level activated: 9.9 minutes)
Section 2.2.
“The above were achieved with the following:
A mid-range SIL2 protection layer which would close the two common jetty
pipeline fail-safe actuated valves (as well as the two common APT pipeline
valves) on initiation of any tank’s high high level switch. This protection layer
has been installed and commissioned and full SIS documentation is available.
The actual credit available from the SIS is calculated as: 2.5 x 10
-3
. See SIS
Design Report SI277001_RPT. The protection layer is auditable via the SIS
maintenance and testing records.”
It was discussed that the 4 pipeline valves are no longer used for the SIL 2 Protection layer as tank-
side import valves have been installed on tanks 561 and 564 and will be installed on tank 568.
This will need to be reflected on the sketch in Appendix 8 of the LOPA.
It was queried whether PL2, the SIL2 system, was applicable for Initiating event 1. To be
investigated. (for all scenarios)
The operational basis of the LOPA was confirmed at the FSA. It was recommended that the above
comments be incorporated in the next revision of the LOPA. This is likely to be when the COMAH
report is updated. (Action 1, expected in 2012)