Siemens 6DR50 Series Operating Instructions Manual page 280

Abbreviations
Abbreviation Long form
OPOS interface Open Positioner Interface
®
PA Process Automation
PDM Process Device Manager
PROFIBUS Process Field Bus
SIA Slit initiator alarm unit
SIL Safety Integrity Level
VDE Verband der Elektrotechnik, Elektro-
nik und Informationstechnik e. V.
VDI Verein Deutscher Ingenieure e. V.
Abbreviation Full term in English
FIT Failure in Time
HFT Hardware Fault Tolerance
MooN "M out of N" voting
MTBF Mean Time Between Failures
MTTR Mean Time To Restoration
PFD Probability of Dangerous Failure on
Demand
PFD Average Probability of Dangerous
AVG
Failure on Demand
SFF Safe Failure Fraction
278
Meaning
Standard interface for the connection between a positioner
and a pneumatic linear or part-turn actuator
Process automation
Siemens communication software / Engineering tool
Fieldbus
-
Safety requirement level as per IEC 61508/IEC 61511
Industrial and professional association
Technical/scientific association
Meaning
Frequency of failure
Number of faults within 10
Hardware fault tolerance:
Capability of a function unit to continue executing a required
function in the presence of faults or deviations.
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" inde-
pendent 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.
Average period between two failures
Average period between the occurrence of a fault in a device or
system and restoration of functionality
Probability of dangerous failures of a safety function on demand
Average probability of dangerous failures of a safety function on
demand
Proportion of safe failures:
Proportion of failures without the potential to bring the safety-
instrumented system into a dangerous or non-permissible func-
tional status.
Operating Instructions, 09/2014, A5E00074631-12
hours
9
SIPART PS2 with and without HART