Siemens ET 200pro - Fail-Safe Shutdown of the ET 200 Pro Standard Edition Modules

Appendix
A.6 Fail-safe shutdown of the ET 200pro Standard edition modules
ET 200pro distributed I/O system
524 Operating Instructions, 03/2013, A5E00335544-08
A.6
Fail-safe shutdown of the ET 200pro Standard edition modules
Introduction
The following structure describes how to implement a fail-safe shutdown of the ET 200pro
Standard modules.
Through the displayed structure (with the safety shutdown device: e.g. 3TK28), all outputs of
the connected ET 200pro Standard edition modules are switched into the safe OFF state.
Safety class SIL2/Category 3 is reached.
Principle of operation
The higher-level safety shutdown device, e.g. 3TK28, disconnects the supplies 2L+ and 2M
(24 V). The ET 200pro Standard edition modules operated on the voltage buses 2L+ and 2M
and their outputs are switched into the safe status. The supply via the 1L+ and 1M bus is not
used by these modules. The connections are not occupied.
Block diagram
Figure A-44 Higher-level safety circuit with safety shutdown device