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Immingham East Terminal – Gasoline Overfill Protection
Safety Instrument System
P & I Design Ltd
DOCUMENT NO: SI277001_RPT
2 Reed Street, Thornaby, UK, TS17 7AF
ISSUE:
F
DATE: 31.10.14
Tel: + 44 (0)1642 617444
PAGE 4 OF 29
Fax: + 44 (0)1642 616447
www.pidesign.co.uk3
DEFINITIONS AND ABBREVIATIONS
The following details the definitions and abbreviations used in this document.
BPCS
Basic Process Control System
Final Element
Part of the SIS which implements the action necessary to achieve a safe
state, e.g. shut off valve
HAZOP
Hazard and Operability Study
Logic Solver
Part of the SIS that performs one or more logic functions, e.g. safety
relay, trip amplifier
Proof Test
Periodic testing to detect failures in a safety instrumented system
Protection Layer
A mechanism that reduces risk by control, prevention or mitigation
Sensor
Part of the SIS which measures the process condition
SIF
Safety instrumented function – An E/E/PE function with a specified
safety integrity level which is necessary to achieve functional safety
SIL
Safety integrity level – A numerical number, 1 to 4 stipulating the level
of integrity the system shall perform to, 1 being the lowest 4 the
highest
SIS
Safety Instrument System – A SIS comprises of sensors, logic solvers
and final elements
1ooN
SIS made up of N independent channels, which are so connected, that
any single channel is sufficient to perform the correct safety
instrumented function
2ooN
SIS made up of N independent channels, which are so connected, that
any two of the channels are required to perform the correct safety
instrumented function
MTBF
Mean Time Between Failures
PFD
Probability of Failing on Demand