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6
GFK-2731 Chapter 6 Connection examples for safe outputs 6-3
6.3 Measures required to achieve a specific safety
integrity level
The safety integrity level (SIL, SIL CL, performance level, and category) that can be
achieved is specified for each connection example.
SIL/SIL CL
When the SIL/SIL CL is specified, the module takes up 1% of the specified SIL/SIL CL.
Performance level
Category In order to actually achieve the specified category, the required measures listed below
must be implemented.
Cat. 2
– Use proven and basic safety principles according to EN ISO 13849-2.
– Use appropriately qualified actuators (see "Requirements for controlled
devices/actuators" on page 2-4).
– Please note that mechanical failure of the switching device can result in the loss of the
safety function.
– Prevent the welding of contacts on the connected contactors or safety relays with
appropriate protection against overcurrent and surge voltage.
– Please note that a single error can result in the loss of the safety function between
tests.
– Ensure that the external wiring is tested by the machine control system on machine
startup and at suitable intervals. This test must detect the loss of the safety function.
– In the event of an error, either safe disconnection must be implemented or a warning
(optical and/or audible) must be generated depending on the application.
Please also refer to "Achievable safety depending on the modules used" on page A-30.
Use the relevant standard to determine the probability of failure in your application
according to EN 61508 (SIL) and EN 62061 (SIL CL).
Table 6-3 PFD and PFH depending on the SIL/SIL CL
PFD PFH
SIL 2/SIL CL 2 1% of 10
-2
1% of 10
-6
SIL 3/SIL CL 3 1% of 10
-3
1% of 10
-7
Use standard EN ISO 13849-1 to determine the performance level in your application.