Description
Required performance level (PLr)
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Required performance level (PLr)
It is necessary to determine the required performance level (PLr) for each
safety function. The required performance level for the previously described
safety function is determined from the risk graph defined by DIN EN ISO
13849-1.
The path through the risk graph depends on how "severity of injury (S)",
"frequency and/or exposure to hazard (F)" and "possibility of avoiding the
hazard (P)" are assessed. The level of each risk situation is categorised in
five levels from "a" to "e"; this is referred to as the performance level (PL).
The control function's contribution to risk reduction is low at PL "a" and high at
PL "e".
Risk graph
Performance level (PLr)
Safety function Required performance level (PLr)
Required performance level to
prevent unexpected start-up of
the conveyor (PLr)
c
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