It is designed and approved suitable for the requirements of :
- Safety Cat. 3 (EN 954-1) / PL “d” (ISO 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)
In order to install and use the Safe Stop function in accordance with the requirements of Safety Cat. 3 (EN 954-1) / PL “d” (ISO 13849-1), the related
information and instructions of the VLT AutomationDrive Design Guide MG.33.BX.YY must be followed! The information and instructions of the Operating
Instructions are not sufficient for a correct and safe use of the Safe Stop functionality!
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
2 Safety Instructions and General Warning
VLT
®
AutomationDrive FC 300 Operating
Instructions
10
MG.33.AG.02 - VLT
®
is a registered Danfoss trademark
2
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