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7 Appendix
7.1 Abbreviations
Table 2: Abbreviations Related to Functional Safety
Number of cycles until 10% of the components have a dangerous failure (for pneumatic and
electromechanical components).
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-related electrical control system
Safety-related parts of control systems
Power Drive System (safety-related)
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.
AQ313340186453en-00101 / 130R054422 | Danfoss A/S © 2021.03
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Safe Torque Off
Operating Guide
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