© 2018 Baker Hughes, a GE company, LLC. All rights reserved.
10 |
=
BHGE
Fail
Annunciation
Undetected
Failure that does not cause a false trip or prevent the safety function
but does cause loss of an automatic diagnostic and is not detected
by another diagnostic.
Fail
Annunciation
Detected
Failure that does not cause a false trip or prevent the safety function
but does cause loss of an automatic diagnostic or false diagnostic
indication.
Fail No Effect
Failure of a component that is part of the safety function but that has
no effect on the safety function.
Low Demand
Mode
Mode where the frequency of demands for operation made on a
safety-related system is no greater than twice the proof test
frequency.
Acronyms
The following acronyms are related to safety functions of the SVI II ESD and are used throughout
this document.
FMEDA
Failure Modes, Effects and Diagnostic Analysis
HFT
Hardware Fault Tolerance
MOC
Management of Change. These are specific procedures often done
when performing any work activities in compliance with government
regulatory authorities.
PFDavg
Average Probability of Failure on Demand
PST
Partial Stroke Test, a test used to detect failure modes in the PST Con-
troller, actuator, and valve assembly.
SFF
Safe Failure Fraction, the fraction of the overall failure rate of a
device that results in either a safe fault or a diagnosed unsafe fault.
SIF
Safety Instrumented Function, a set of equipment intended to reduce
the risk due to a specific hazard (a safety loop).
SIL
Safety Integrity Level, discrete level (one out of a possible four) for
specifying the safety integrity requirements of the safety functions to
be allocated to the E/E/PE safety-related systems where Safety
Integrity Level 4 has the highest level of safety integrity and Safety
Integrity Level 1 has the lowest.
SIS
Safety Instrumented System – Implementation of one or more Safety
Instrumented Functions. A SIS is composed of any combination of
sensor (s), logic solver (s), and final element (s).
