Abbreviations
B.1 List of abbreviations
SIPART PS2 with PROFIBUS communication
274
Operating Instructions, 09/2007, A5E00127926-07
Abbreviation
Long form
Meaning
PDM
Process device manager
Siemens communication software / engineering tool
PROFIBUS
Process field bus
Fieldbus
PTB
Physikalisch Technische
Bundesanstalt
-
SIA
Slotted initiator alarm unit
-
SIL
Safety integrity level
Safety requirement level as per IEC 61508/IEC 61511
VDE
Verband der Elektrotechnik,
Elektronik und Informationstechnik
e.V.
Industrial and professional association
VDI
Verein Deutscher Ingenieure e.V.
Technical-scientific association
Abbreviation
Full term in English
Meaning
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.
MTBF
Mean Time Between Failures
Average period between two failures
MTTR
Mean Time To Repair
Average period between the occurrence of a fault in a device or
system and the repair
PFD
Probability of Failure on Demand
Probability of dangerous failures of a safety function on demand
PFD
AVG
Average Probability of 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.
SIL
Safety Integrity Level
The international standard IEC 61508 defines four discrete
Safety Integrity Levels (SIL 1 to SIL 4). Each level corresponds
to a range of probability for failure of a safety function. The
higher the Safety Integrity Level of the safety-instrumented
system, the lower the probability that it will not execute the
required safety functions.
SIS
Safety Instrumented System
A safety-instrumented system (SIS) executes the safety
functions that are required to achieve or maintain a safe status
in a system. It consists of a sensor, logic unit/control system
and final controlling element.
FIT
Failure in Time
Frequency of failure
Number of faults withing 10
9
hours
TI
Test Interval
Testing interval of the protective function