ABB ACH580-31, Hardware Manual

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Description Reference Term or
abbreviation
Mean time to dangerous failure: (Total number of life
units) / (Number of dangerous, undetected failures)
during a particular measurement interval under stated
conditions EN ISO 13849-1 MTTFD
Average probability of dangerous failure on demand,
that is, mean unavailability of a safety-related system to
perform the specified safety function when a demand
occurs IEC 61508 PFDavg
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 61508 PFH
Average frequency of dangerous failures per hour for the
diagnostic function of STO IEC/EN 62061 PFHdiag
Performance level. Levels a…e correspond to SIL EN ISO 13849-1 PL
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 61508 SC
Safe failure fraction (%) IEC 61508 SFF
Safety integrity level (1…3) IEC 61508 SIL
Safe torque off IEC/EN 61800-5-2 STO
Proof test interval. T1 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
T1 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 T1
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
TM values given cannot be regarded as a guarantee
or warranty.
EN ISO 13849-1
TM
Dangerous failure rate (per hour) of the diagnostics
function of STO IEC 61508-6 λDiag_d
Safe failure rate (per hour) of the diagnostics function
of STO IEC 61508-6 λDiag_s
The Safe torque off function 239