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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 11 OF 23
Fax: + 44 (0)1642 616447
www.pidesign.co.uk6.2.3 Safety Relay
Tag Numbers R252, R292, R332, R372, R492, R523, R572, R612, R652, R692. Note: No
Safety Relays on Additive Tanks.
The chosen relay is PNOZ S2 which has the following safety requirements:
The circuit is redundant with built in self monitoring
The safety function remains effective in the case of component failure
The correct opening and closing of the safety function is tested automatically in each
on-off cycle
Electronic fuse
The relay has the following features:
3 positively guided normally open safety contacts
Status indicators
Feedback control loop for monitoring of external switches
Feedback control loop in series with reset circuit
The relay is also fail safe on power failure i.e. safety contacts normally open.
From the Pilz Safety Relay Type PNOZ S2 Internal safety Integrity Details, the PFD is taken
as 2.13 x 10
-5
.
6.2.4 Logic Solver Subsystem Summary
The combined PFD for the logic solver subsystem is 3.98 x 10
-4
+ 2.13 x 10
-5
= 4.20 x 10
-4
From the enclosed calculations the sub-system meets the requirements of >SIL 2 with a
PFD
G
of 4.207 x 10
-4