Festo CMTT-AS S1 Series, Description, Page: 35 / 46

Safety reference data for the safety sub-function SBC
Wiring Two brakes
1)
with SBA evalu-
ation
2)
One brake
3)
without SBA evalu-
ation
Hardware fault toler-
ance in accordance
with EN 61508, HFT 1 0
Common cause factor
for dangerous undetec-
ted failures
β
in accord-
ance with EN 61508
[%] 5
Classification in
accordance with
EN 61508 Type A
1) One brake connected to BR+/BR− and a second brake connected to BR-EXT; 2-channel wiring and request via #SBC-A and #SBC-B.
2) Safety sub-function monitored by the safety controller via the SBA diagnostic output at least 1 x every 24 h.
3) Brake connected either to BR+/BR− or to BR-EXT; 1-channel request via the safety controller using #SBC-A and #SBC-B; both inputs
must be bridged externally.
Tab. 16 Safety reference data for the safety sub-function SBC
Remarks
– Depending on the desired safety classification, evaluation of the SBA diagnostic output by the
safety relay unit is either mandatory or optional.
– To achieve the safety classification Cat. 3, PL d, SIL 2 (or also Cat. 2, PL c/d) in connection with 2
brakes, evaluation of the SBA diagnostic output is mandatory.
– If you require an SBC function with a classification higher than Cat. 1, PL c, the diagnostic outputs
must be checked regularly – at least 1 x once every 24 h – by having them tested automatically by
the safety relay unit (
è
EN ISO 13849-1, Annex G.2).
– The safety relay unit must request the safety sub-function at least once within 24 h and thereby
monitor the SBA diagnostic output to achieve a diagnostic coverage of at least 60 %. If the signal
behaviour does not correspond to expectations, the system must be put into a safe condition
within the reaction time. It is essential that time monitoring be provided in the safety controller.
The technical data for the safety sub-function SS1 must be calculated individually according to the
application. Use the specified safety reference data for STO and SBC for the calculation.
Technical data
35 Festo — CMMT-AS-...-S1 — 2018-10a