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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.
SIL/
Frame size
PL
SILCL
R8i
3
e
2×R8i
3
e
3×R8i
3
e
4×R8i
3
e
5×R8i
3
e
6×R8i
3
e
7×R8i
3
e
8×R8i
3
e
• 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 B 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.
• STO response times:
• STO reaction time (shortest detectable break): 1 ms
• STO response time: 2 ms (typical), 25 ms (maximum)
• Fault detection time: Channels in different states for longer than 200 ms
• Fault reaction time: Fault detection time + 10 ms
• Indication delays:
• STO fault indication (parameter 31.22) delay: < 500 ms
• STO warning indication (parameter 31.22) delay: < 1000 ms
PFH
SFF
PFD
avg
(T
= 20 a)
1
(%)
(T
= 2 a)
1
(1/h)
>99
5.0E-11
4.5E-07
>99
6.2E-11
5.5E-07
>99
7.3E-11
6.5E-07
>99
8.4E-11
7.6E-07
>99
9.5E-11
8.6E-07
>99
1.1E-10
9.6E-07
>99
1.2E-10
1.1E-06
>99
1.3E-10
1.2E-06
The Safe torque off function 97
PFD
MTTF
DC
avg
D
(T
= 5 a)
(a)
(%)
1
1.1E-06
23970
≥90
1.3E-06
16330
≥90
1.6E-06
12390
≥90
1.9E-06
9980
≥90
2.1E-06
8360
≥90
2.4E-06
7190
≥90
2.6E-06
6310
≥90
2.8E-06
5620
≥90
T
M
Cat.
SC
HFT
CCF
(a)
3
3
1
80
20
3
3
1
80
20
3
3
1
80
20
3
3
1
80
20
3
3
1
80
20
3
3
1
80
20
3
3
1
80
20
3
3
1
80
20
3AXD10000078136 F
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