Emerson Rosemount 5900 Safety Manual page 39

Safety Manual
00809-0400-5100, Rev AB
Appendix B
Table B-1. Terms Used in Safety Instrumented Systems
Term
BPCS
Demand rate
FIT
FMEDA
HFT
High mode of operation
LAHH
Low mode of operation
Mode of operation
PFD
avg
PFH (average frequency of
a dangerous failure per
hour)
SFF
SIF
SIL
SIS
Type B component
1oo1D
Terms and Definitions
Terms and Definitions
Description
Basic Process Control System
How often it will be required from a safety integrity system (or the
safety function) to react on inputs from process to bring it into a safe
state, i.e. to issue an alarm
Failure in Time (1 FIT = 1failure/10
Failure Modes, Effects and Diagnostics Analysis
Hardware Fault Tolerance
The safety function is only performed on demand, in order to
transfer the EUC into a specified safe state, and the frequency of
demands is greater than one per year
Level Alarm High High
The safety function is only performed on demand, in order to
transfer the EUC into a specified safe state, and the frequency of
demands is no greater than one per year
The way in which a safety function operates, which may be either
low mode of operation or high mode of operation
Average probability of Failure on Demand
Average frequency of a dangerous failure of an E/E/PE safety related
system to perform the specified safety function over a given period
of time
Safe Failure Fraction summarizes the fraction of failures, which lead
to a safe state and the fraction of failures which will be detected by
diagnostic measures and lead to a defined safety action.
Safety Instrumented Function
Safety Integrity Level
Safety Instrumented System
Complex component (using micro controllers or programmable
logic)
Architecture consisting of a single channel with additional
diagnostic capabilities.
Terms and Definitions
November 2019
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