Information
The safety-related figures mentioned in this safety manual are only valid if all the
conditions stipulated in this safety manual and the mentioned activities are respected.
The PFD values specified in this safety manual are only examples and subject to
certain assumptions e.g. on T
proof
, MTTR, …
The PFD calculation should always be performed individually for each system using
the parameters and conditions applicable for the respective system. The
λ
DU
and
λ
DD
values should be used as input. When observing the proof test procedures indic-
ated in this safety manual, we recommend using a proof test coverage (PTC) of 90
% for the calculations.
9.2.
Specific parameters for AC 01.2 actuator controls in SIL version with actuators of SQ .2 series
The following parameter tables provide the safety figures for the different versions.
If one or several of the assumptions indicated below are changed, you have to
recalculate the probability of failure PFD in particular but possibly also other
parameters.
When determining the PFD values, please note that the stipulated proof test cannot
fully restore the system. For this reason, the following data is used for calculation:
●
PTC = 90 % (proof test coverage rate [%])
●
T
1
= 1 year (proof test interval [h])
●
T
2
= 10 years (requirement interval = lifetime [h])
●
MRT = 72 hours (mean repair time [h])
●
Td_ESD = 730 hours
(diagnostic test interval of actuator monitoring (for safety function Safe ESD
[h])
●
Td_ESD_AVG = 365 hours (mean duration for failure detection))
●
Td_STOP = 0 hours (diagnostic test interval [h])
●
MTTR_ESD = 437 hours
●
MTTR_STOP = 72 hours
The following formula can be used for the calculation of the PFD
avg
values:
Information
The figures for Safe STOP OPEN or Safe STOP CLOSE, indicated in the subsequent
tables, refer to one of the two functions. If a general Safe STOP (inhibit operation in
both directions) is to be performed while activating the functions Safe STOP OPEN
and Safe STOP CLOSE at the same time, the double failure rate of the respective
individual functions (Safe STOP OPEN/CLOSE) must be applied for the assessment.
Table 9: SQ .2/SQEx .2 type range with AC 01.2/ACExC 01.2 actuator controls in
SIL version
SQ 05.2 – SQ 12.2 / SQEx 05.2 – SQEx 12.2
Switchgear version: Contactors
Safe STOP OPEN or Safe
STOP CLOSE
Safe ESD
Safety function
636 FIT
185 FIT
λ
S
89 FIT
821 FIT
λ
DD
1)
269 FIT
213 FIT
λ
DU
72 %
82 %
SFF
24 %
79 %
DC
40
Part-turn actuators
Safety-related figures
with AC 01.2-SIL/ACExC 01.2-SIL
