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Contrinex Industrial Electronics
4. Evaluate the achieved Performance Level
5. Verify the achieved Performance Level
6. Validate that all requirements are met
Based on risk identification, the required performance level of risk re-
duction is determined using the following graph sourced from EN/ISO
13849-1, Annex A.
The objective is to determine the required performance level PL
r
that
sets the requirements of the necessary safety system, depending on
the risks involved in each case. As described below, three parameters
are taken into consideration:
1. The potential severity of the harm
2. The frequency and/or duration of exposure to the hazard
3. The possibility of avoiding the hazard
DIAGRAM 2: REQUIRED PERFORMANCE LEVEL
PL
r
L
H
P2
F2
S2
P1
P2
F1
P1
P2
F2
S1
1
P1
F1
P2
P1
a
b
c
d
e
1
starting point for evaluation of safety function contribution to risk reduction
S
severity of injury:
S1
slight (normally reversible injury)
S2
serious (normally irreversible injury or death)
F
frequency and/or exposure to hazard:
F1
seldom-to-less-often and/or exposure time is short
F2
frequent-to-continuous and/or exposure time is long
P
possibility of avoiding hazard or limiting harm:
P1
possible under specific conditions
P2
scarcely possible
PL
r
required performance level
Low contribution to
risk reduction
High contribution
to risk reduction
In order to reduce the determined risk (PL
r
) to an appropriate level, a
safety system with performance level PL
≥
PL
r
needs to be properly
implemented. A corresponding average probability of dangerous failure
per hour (PFH
D
) can be associated with each performance level :
