Safety data
The safety data for the Safe torque off function is given below.
Note: The safety data is calculated for redundant use, and does not apply if both STO
channels are not used.
T
M
(a)
CCFHFTSCCat.
DC
(%)
MTTF
D
(a)
PFD
avg
(T
1
= 5 a)
PFD
avg
(T
1
= 2 a)
PFH
(T
1
= 20 a)
(1/h)
SFF
(%)
PL
SIL/
SILCL
Frame size
2080133≥90242937.08E-052.83E-053.23E-0998.8e3
R1i
R2i
R3i
R4i
2080133≥90169466.27E-052.51E-053.36E-0996.7e3R5i
2080133≥9065388.47E-053.39E-053.87E-0999.0e3
R6i
R7i
2080133≥90239701.1E-064.5E-075.0E-11>99e3R8i
2080133≥90163301.3E-065.5E-076.2E-11>99e32×R8i
2080133≥90123901.6E-066.5E-077.3E-11>99e33×R8i
2080133≥9099801.9E-067.6E-078.4E-11>99e34×R8i
2080133≥9083602.1E-068.6E-079.5E-11>99e35×R8i
2080133≥9071902.4E-069.6E-071.1E-10>99e36×R8i
2080133≥9063102.6E-061.1E-061.2E-10>99e37×R8i
2080133≥9056202.8E-061.2E-061.3E-10>99e38×R8i
2080133≥9050603.1E-061.3E-061.4E-10>99e39×R8i
2080133≥9046103.3E-061.4E-061.5E-10>99e310×R8i
3AXD10000041323 F, 3AXD10000078136 F
• The following temperature profile is used in safety value calculations:
•
670 on/off cycles per year with ΔT = 71.66 °C
•
1340 on/off cycles per year with ΔT = 61.66 °C
•
30 on/off cycles per year with ΔT = 10.0 °C
• 32 °C board temperature at 2.0% of time
• 60 °C board temperature at 1.5% of time
• 85 °C board temperature at 2.3% of time.
• The STO is a type A (frames R1i…R7i) or type B (frame R8i and multiples) safety
component as defined in IEC 61508-2.
• Relevant failure modes:
• The STO trips spuriously (safe failure)
• The STO does not activate when requested
• A fault exclusion on the failure mode “short circuit on printed circuit board” has been
made (EN 13849-2, table D.5). The analysis is based on an assumption that one
failure occurs at one time. No accumulated failures have been analyzed.
The Safe torque off function 197
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