6 safety manual – JUMO 701150 14597 safetyM STB/STW - Safety Temperature Limiter and Safety Temperature Monitor Operating Manual User Manual
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6 Safety Manual
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6.11.3
Contribution to risk minimization through the control system
The objective of compliance with the overall draft procedure for the machine is to achieve the safety objectives (see 4.1). The
draft of the SRP/CS to provide the required risk minimization is an integral part of the overall draft procedure for the machine.
The SRP/CS provides the safety function(s) with a PL that achieves the required risk minimization. Through the provision of
safety functions, either as an inherently safe part of the construction or as the control of a protective guard or protective device,
the design of the SRP/CS is part of the risk minimization strategy. This is an iterative process and is depicted in images 1 and
3.
The features of each safety function (see section 5) and the required Performance Level must be described and documented in
the specification of the safety requirements.
In this part of DIN EN ISO 13849, the Performance Levels are defined in the form of the probability of a dangerous failure per
hour. Five Performance Levels (a to e) are specified with defined areas of the probability of a dangerous failure per hour (see ta-
ble).
Performance Level (PL)
Average probability
of a dangerous failure per hour 1/h
a
≥
10
-5
to < 10
-4
b
≥
3 Þ 10
-6
to < 10
-5
c
≥
10
-6
to < 3 × 10
-6
d
≥
10
-7
to < 10
-6
e
≥
10
-8
to < 10
-7
NOTE: in addition to the average probability of a dangerous failure per hour, further measures are required to achieve the PL.