Danfoss VLT FC Series Operating Manual page 22

Safe Torque Off
Operating Guide
7 Appendix
7.1 Abbreviations
Table 2: Abbreviations Related to Functional Safety
Abbrevia- Reference
tions
B
10d
Cat. EN ISO 13849-1
CCF
DC
FIT
HFT EN IEC 61508
MTTFd EN ISO 13849-1
PFH EN IEC 61508
PFD EN IEC 61508
PL EN ISO 13849-1
PLr
SIL
EN IEC 61508
EN IEC 62061
STO EN IEC 61800-5-2
SS1 EN IEC 61800-5-2
SRECS EN IEC 62061
SRP/CS EN ISO 13849-1
PDS/SR EN IEC 61800-5-2
7.2 Conventions
• Numbered lists indicate procedures.
• Bulleted and dashed lists indicate listings of other information where the order of the information is not relevant.
• Bolded text indicates highlighting and section headings.
• Italicized text indicates the following:
- Cross-reference.
- Link.
- Footnote.
- Parameter name.
22 | Danfoss A/S © 2021.03
Description
Number of cycles until 10% of the components have a dangerous failure (for pneumatic and
electromechanical components).
Category, level "B, 1–4"
Common cause failure
Diagnostic coverage divided into Low, Medium, and High.
Failure in time: 1E-9/hour
Hardware fault tolerance: HFT = n means that n+1 faults could cause a loss of the safety func-
tion.
Mean time to failure - dangerous. Unit: Years are divided into Low, Medium, and High.
Probability of dangerous failures per hour. Consider this value if the safety device is operated
in high demand or continuous mode of operation, where the frequency of demands for oper-
ation made on a safety-related system is greater than 1 per year.
Average probability of failure on demand, value used for low demand operation.
Discrete level used to specify the ability of safety-related parts of control systems to perform a
safety function under foreseeable conditions. Levels divided into a to e.
Required performance level (the required performance level for a particular safety function).
Safety integrity level
Safe Torque Off
Safe Stop 1
Safety-related electrical control system
Safety-related parts of control systems
Power Drive System (safety-related)
Appendix
AQ313340186453en-00101 / 130R0544