DescriptionReferenceTerm or ab-
breviation
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
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 con-
dition
IEC 61508, IEC
62061
Proof test
Systematic capabilityIEC 61508SC
Safe failure fraction (%)IEC 61508SFF
Safety integrity level (1…3)IEC 61508SIL
Maximum SIL (level 1…3) that can be claimed for a safety
function or subsystem
IEC/EN 62061SILCL
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
￭ TÜV certificate
The TÜV certificate is available on the Internet at www.abb.com/drives/documents.
The Safe torque off function 201
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