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•
STO reaction time (shortest detectable break): 1 ms
•
STO response time: 2 ms (typical), 5 ms (maximum)
•
Fault detection time: Channels in different states for longer than 200 ms
•
Fault reaction time: Fault detection time + 10 ms
•
STO fault indication (parameter 31.22) delay: < 500 ms
•
STO warning indication (parameter 31.22) delay: < 1000 ms
Abbreviations
Abbr.
Reference
Cat.
EN ISO 13849-1
CCF
EN/ISO 13849-1
DC
EN/ISO 13849-1
FIT
IEC 61508
HFT
IEC 61508
MTTF
EN/ISO 13849-1
D
PFD
IEC 61508
avg
PFH
IEC 61508
PL
EN/ISO 13849-1
SC
IEC 61508
SFF
IEC 61508
SIL
IEC 61508
SILCL
IEC/EN 62061
SS1
EN 61800-5-2
STO
EN 61800-5-2
T1
IEC 61508-6
Description
Classification of the safety-related parts of a control system in respect
of their resistance to faults and their subsequent behavior in the fault
condition, and which is achieved by the structural arrangement of the
parts, fault detection and/or by their reliability. The categories are: B, 1,
2, 3 and 4.
Common cause failure (%)
Diagnostic coverage
Failure in time: 1E-9 hours
Hardware fault tolerance
Mean time to dangerous failure: (The total number of life units) / (the
number of dangerous, undetected failures) during a particular
measurement interval under stated conditions
Average probability of dangerous failure on demand
Average frequency of dangerous failures per hour
Performance level. Levels a...e correspond to SIL
Systematic capability
Safe failure fraction (%)
Safety integrity level (1...3)
Maximum SIL (level 1...3) that can be claimed for a safety function or
subsystem
Safe stop 1
Safe torque off
Proof test interval. T1 is a parameter used to define the probabilistic
failure rate (PFH or PFD) for the safety function or subsystem.
Performing a proof test at a maximum interval of T1 is required to keep
the SIL capability valid. The same interval must be followed to keep the
PL capability (EN ISO 13849) valid. Note that any T1 values given
cannot be regarded as a guarantee or warranty.
See also section
Maintenance
Safe torque off function 151
(page 105).
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