DescriptionReferenceTerm or
abbreviation
Average frequency of dangerous failures per hour, that
is, average frequency of a dangerous failure of a safety
related system to perform the specified safety function
over a given period of time
IEC 61508PFH
Average frequency of dangerous failures per hour for the
diagnostic function of STO
IEC/EN 62061PFH
diag
Performance level. Levels a…e correspond to SILEN ISO 13849-1PL
Periodic test performed to detect failures in a
safety-related system so that, if necessary, a repair can
restore the system to an "as new" condition or as close
as practical to this condition
IEC 61508, IEC
62061
Proof test
Systematic capability (1…3)IEC 61508SC
Safe failure fraction (%)IEC 61508SFF
Safety integrity level (1…3)IEC 61508SIL
Safe torque offIEC/EN 61800-5-2STO
Proof test interval.
T
1
is a parameter used to define the
probabilistic failure rate (PFH or PFD) for the safety
function or subsystem. Performing a proof test at a
maximum interval of
T
1
is required to keep the SIL
capability valid. The same interval must be followed to
keep the PL capability (EN ISO 13849) valid.
IEC 61508-6
T
1
See also section Maintenance.
Mission time: the period of time covering the intended
use of the safety function/device. After the mission time
elapses, the safety device must be replaced. Note that
any
T
M
values given cannot be regarded as a guarantee
or warranty.
EN ISO 13849-1
T
M
Dangerous failure rate (per hour) of the diagnostics
function of STO
IEC 61508-6λ
Diag_d
Safe failure rate (per hour) of the diagnostics function
of STO
IEC 61508-6λ
Diag_s
￭
TÜV certificate
The TÜV certificate is available on the Internet.
The Safe torque off function 179
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