Technical specifications
9.4 Fail-safe mode
KP8, KP8F, KP32F
Operating Instructions, 11/2011, A5E03284305-02
111
Power supply
Parameter Value Comment
Hardware Fault Tolerance 0 –
Classification A –
Architecture 1oo1D –
Failure mode
• Detected
• Undetected
Dangerous process value
• 22.50 FIT
• 0.22 FIT
Due to failures in the power supply
Failure Mode Diagnostic
• Detected
• Undetected
No error signaling or no safe
values
• 0 FIT
• 0 FIT
Calculation according
IEC 13849-1, CAT4
Diagnostic Coverage 99.03 % –
Diagnostic test interval < 10 ms Voltage monitoring in hardware
Safe Failure Fraction 99.84 % –
Fail-safe mode for 1oo1 evaluation
● According to IEC 61508
Systematic Capability SIL3
Mode of operation High and low demand mode
Meantime to Restoration (MTTR) 100 h
Probability of a dangerous failure per hour
(PFH)
5.95 × 10
–10
1/h
Probability of a dangerous failure on demand
(PFD)
2.61 × 10
–5
Safe Failure Fraction (SFF) 99.19 %
Diagnostic test interval 15 ms
Proof Test Interval 10 y
Lifetime 10 y
● According to IEC 13849-1
Meantime to Failure (MTTF
d
) 560 y
Meantime to Restoration (MTTR) 100 h
Diagnostic Coverage (DC
avg
) 98.90 %
Performance Level d
Category 3
● According to EN 954-1
Category 3
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