LF364001_MNL - Overfill Protection SIS Design Manual

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Local Fuel – The Shoreham Oil Terminal
Gasoline Import - Safety Instrument System
P & I Design Ltd DOCUMENT NO: LF364006_RPT
2 Reed Street, Thornaby, UK, TS17 7AF ISSUE: C DATE: 13.05.16
Tel: + 44 (0)1642 617444 PAGE 15 OF 23
Fax: + 44 (0)1642 616447
Tank 1
Maximum Capacity 2333 m3
Level switch operation : 98.6% of tank capacity 2300 m3
Capacity remaining in tank at point High High level activated 33 m3
Process safety time (33m3 / 400m3/h) 5 mins
Tank 2
Maximum Capacity 1158 m3
Level switch operation : 97% of tank capacity 1124 m3
Capacity remaining in tank at point High High level activated 34 m3
Process safety time (34m3 / 400m3/h) 5 mins
Tank 3
Maximum Capacity 1685 m3
Level switch operation : 98% of tank capacity 1652 m3
Capacity remaining in tank at point High High level activated 33 m3
Process safety time (33m3 / 400m3/h) 5 mins
Tank 4
Maximum Capacity 2345 m3
Level switch operation : 98.6% of tank capacity 2311 m3
Capacity remaining in tank at point High High level activated 34 m3
Process safety time (34m3 / 400m3/h) 5 mins
The above figures are based on the Local Fuel LOC sheet
The valve will therefore be set to close in a time > 80 secs for surge protection (90s±10%)
and < 2mins 30s to prevent overfill (process safety time / 2)
Rotork skilmatic, the actuator manufacturer, quote the following data based on an Sira IEC
61508 certificate for a SI2.1Q actuator:
λSU = 1.83 x 10 -6 hours
λDU = 2.66 x 10-7 hours
PFd calculated is 1.17 x 10-3 based on a mean time to repair of 24 hours and a proof test
interval of 12 months.
SFF calculated is 87%
Pekos, the proposed valve manufacturer, quote the following data based on an Exida IEC
61508 certificate.:
λs = 1650 x 10-9 hours
λDD = 292 x 10-9 hours
λDU = 334 x 10-9 hours
PFd calculated is 1.48 x 10-3 based on a mean time to repair of 24 hours and a proof test
interval of 12 months.