JUMO dTRANS T06 - Risk Reduction through the Control System

6 Safety Manual
48
The following chart can be used to determine the PL if the MTTF
d
value of the sensor is 100 years. The reached DC for identi-
fying the errors of the sensor of the temperature transmitter will be calculated at (HFT = 1) with ≥ 60% in a redundant applica-
tion.
6.7.4 Risk reduction through the control system
In order to meet safety aims for the machine, the entire design process must be followed. The design of the SRP/CS (safety-re-
lated part of a control system) is a necessary part of the entire design process in order to provide the risk reduction required.
This can only be achieved with a PL that achieves the required risk reduction. By installing a protective guard or protective de-
vice, the design of the SRP/CS is part of the risk reduction strategy.
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 13849-1, the performance levels are defined in the form of the probability of a dangerous failure per
hour. Five performance levels (a to e) have been specified (see Table).
PL of the used Sensor
MTTF
d
=100 years
max. achievable PL of the system
with 1oo1 architecture
max. achievable PL of the system in
redundant use (HFT = 1) DC ≥ 60%
bb d
cc d
dc d
ec d
Performance level (PL) Average probability
of a dangerous failure per hour 1/h
a ≥ 10
-5
to < 10
-4
b ≥ 3 × 10
-6
to < 10
-5
c ≥ 10
-6
to < 3 × 10
-6