Emerson ROSEMOUNT 5300 - Appendix A Terms and Definitions

A Terms and definitions
Table A-1: Terms and Definitions
Term Definition
BPCS Basic Process Control System
DU Dangerous Undetected
Diagnostic test interval The time from when a dangerous failure/condition occurs
until the device has set the safety related output in a safe
state (total time required for fault detection and fault
reaction).
FIT Failure In Time per billion hours
FMEDA Failure Modes, Effects and Diagnostic Analysis
HART
®
Highway Addressable Remote Transducer
HFT Hardware Fault Tolerance
High demand mode The safety function is only performed on demand, in order
to transfer the EUC (Equipment Under Control) into a
specified safe state, and where the frequency of demands
is greater than one per year (IEC 61508-4).
Low demand mode The safety function is only performed on demand, in order
to transfer the EUC into a specified safe state, and where
the frequency of demands is no greater than one per year
(IEC 61508-4).
PFD
AVG
Average Probability of Failure on Demand
Proof test coverage factor The effectiveness of a proof test is described using the
coverage factor which specifies the share of detected
dangerous undetected failures (λ
DU
). The coverage factor
is an indication of a proof test’s effectiveness to detect
dangerous undetected faults.
Safety deviation The maximum allowed deflection of the safety output due
to a failure within the device (expressed as a percentage of
span).
Any failure causing the device output to change less than
the Safety Deviation is considered as a "No Effect" failure.
All failures causing the device output to change more than
the Safety Deviation and with the device output still within
the active range (non-alarm state) are considered
dangerous failures.
Note that the Safety Deviation is independent of the
normal performance specification or any additional
application specific measurement error.
SFF Safe Failure Fraction
SIF Safety Instrumented Function
Safety Manual Terms and definitions
00809-1900-4530 September 2020
Rosemount 5300:SIS Level Transmitter 43