CONTROL UNIT SERIES AUS X
4
8540643 - 26/08/2016 Rev.13
NEW SAFETY PARAMETERS FOR TYPE 2 BARRIERS AND
MANDATORY LABELLING
With the publication of Edition 3 of the harmonized EN 61496-1
standard it is no longer possible to use a Type 2 safety light barrier
for safety functions assessed as SIL 2 / PL d.
If a safety level of SIL 2 / PL d (or higher) is required and it is
nevertheless intended to use a safety light barrier, then it will be
necessary to use a Type 4 safety light barrier.
This regulatory requirement derives from the fact that the reduction of
risk that can be obtained via a photoelectric safety barrier is not only
a function of the safety level of its electronic parts, but is also
determined
by
its
systematic
capabilities
(for
example:
environmental influences, EMC, optical performance and detection
principle).
The systematic capability of a Type 2 photoelectric barrier may in fact
not be sufficient to ensure adequate risk reduction for SIL 2 / PL d
applications.
The standard also establishes that the labelling of Type 2 safety
barriers must indicate such limitation to SIL 1 / PL c.
The PFHd values declared for the electronic control part of the
device, on the other hand, are not limited and therefore it is possible
to use the PFHd value provided by the manufacturer of the device in
the global assessment of the safety function, even if it exceeds the
SIL 1 / PLc range.
