3.12 Safe Stop of AF-650 GP
The AF-650 GP can perform the safety function Safe Torque Off (As defined by IEC 61800-5-2) or Stop Category 0 (as defined in EN 60204-1).
It is designed and approved suitable for the requirements of :
- Safety Category 3 in EN 954-1 (and ISO EN 13849-1)
- Performance Level "d" in ISO EN 13849-1
- SIL 2 Capability in IEC 61508 and EN 61800-5-2
- SILCL 2 in EN 61062
This functionality is called Safe Stop. Prior to integration and use of Safe Stop in an installation, a thorough risk analysis on the installation must be carried out in
order to determine whether the Safe Stop functionality and safety levels are appropriate and sufficient.
After installation of Safe Stop, a commissioning test as specified in section Safe Stop Commissioning Test of the Design Guide must be performed.
A passed commissioning test is mandatory for fulfilment of Safety Cat. 3 (EN 954-1) / PL “d” (ISO 13849-1)
The following values are associated to the different types of safety levels:
Performance Level "d":
- MTTFD (Mean Time To Dangerous Failure): 24816 years
- DC (Diagnstic Coverage): 99,99%
- Category 3
SIL 2 Capability, SILCL 2:
- PFH (Probability of Dangerous failure per Hour) = 7e-10FIT = 7e-19/h
- SFF (Safe Failure Fraction) > 99%
- HFT (Hardware Fault Tolerance) = 0 (1oo1D architecture)
Abbreviations related to Functional Safety
Abbreviation Reference Description
Cat. EN 954-1 Safety category, levels 1-4
FIT Failure In Time: 1E-9 hours
HFT IEC 61508 Hardware Fault Tolerance: HFT = n means, that n+1 faults could cause a loss of the safety function
MTTFd EN ISO 13849-1 Mean Time To dangerous Failure: (The total number of life units) / (the number of dangerous, undetected
failures), during particular measurement interval under stated conditions
PFHd IEC 61508 Probability of Dangerous Failures per Hour. This value shall be considered if the safety device is operated
in high demand (more often than once per year) or continuous mode of operation, where the frequency
of demands for operation made on a safety-related system is greater than one per year or greater than
twice the proof-test frequency.
PL EN ISO 13849-1 Performance Level: Corresponds SIL, Levels a-e
SFF IEC 61508 Safe Failure Fraction [%] ; Percentage part of safe failures and dangerous detected failures of a safety
function or a subsystem related to all failures.
SIL IEC 61508 Safety Integrity Level
STO EN 61800-5-2 Safe Torque Off
AF-650 GP Design Guide
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