Siemens SITRANS P DS III - Functional Safety Abbreviations

List of abbreviations/acronyms
B.2 Functional safety
SITRANS P DS III with PROFIBUS PA
246 Operating Instructions, 06/2013, A5E00053276-07
Abbreviation
In full
Meaning
PA Process automation Protocol for the transmission of information between field device
and automation system over the PROFIBUS.
PDM
Process Device Manager
PN
Pressure Nominal
Nominal pressure measured in bars
PNO
PROFIBUS user organization
PROFIBUS Process Field Bus Manufacturer-independent standard for the networking of field
devices, e.g. PLC, drives, or sensors. PROFIBUS can be used with
the protocols DP or PA.
SELV Safety extra-low voltage
Safety extra-low-voltage
B.2
Functional safety
Abbreviation
Full term in English
Meaning
CFC Continuous Function Chart Software package for graphical, technology-oriented
configuration of automation tasks
FIT Failure in Time Frequency of failure
Number of faults withing 10
9
hours
HFT Hardware Fault Tolerance Hardware fault tolerance:
Capability of a function unit to continue executing a required
function in the presence of faults or deviations.
MooN "M out of N" voting Classification and description of the safety-instrumented system
in terms of redundancy and the selection procedures used.
A safety-instrumented system or part that consists of "N"
independent channels. The channels are connected to each
other in such a way that "M" channels are in each case
sufficient for the device to perform the safety instrumented
function.
Example:
Pressure measurement: 1oo2 architecture. A safety-
instrumented system decides that a specified pressure limit has
been exceeded if one out of two pressure sensors reaches this
limit. In a 1oo1 architecture, there is only one pressure sensor.
MTBF
Mean Time Between Failures
Average period between two failures
MTTR Mean Time To Restoration Average period between the occurrence of a fault in a device or
system and restoration of functionality
PFD Probability of Dangerous Failure on
Demand
Probability of dangerous failures of a safety function on demand
PFD
AVG
Average Probability of Dangerous
Failure on Demand
Average probability of dangerous failures of a safety function on
demand
SFF Safe Failure Fraction Proportion of safe failures:
Proportion of failures without the potential to bring the safety-
instrumented system into a dangerous or non-permissible
functional status.