Machine & Operator Safety
Fail-safe distributed I/O modules
May 4, 2012 by Manufacturing AUTOMATION
The Siemens Industry Automation Division has developed three fail-safe modules for the Simatic ET 200iSP intrinsically safe distributed I/O system. The new modules 8F-DI Ex Namur, 4F-DO Ex 40mA/17.4V and 4F-AI Ex Hart meet the high safety requirements in accordance with the relevant standards such as IEC 61508 to SIL 3. This means that, integrated into the Simatic ET 200iSP distributed I/O system, they can be used directly without Ex barrier up to Ex Zone 1/21. The connected intrinsically safe sensors and actuators can be run into Ex Zone 0/20. The new modules are suitable for applications such as ESD (emergency shutdown), boiler protection, or fire and gas equipment. For fire and gas applications, the new modules have the important diagnostics functions “Last valid value” and “Energize-to-trip.” The intrinsically safe Profibus version is used for communication between the Simatic ET 200iSP distributed I/O system and the higher-level controllers. The same cable is used here for transferring the standard automation data and the fail-safe signals in accordance with the Profisafe profile. The Simatic ET 200iSP is configured with the Step 7 engineering tool. Off-the-shelf, TÜV-certified library blocks are available in the Step 7 option packages Distributed Safety and S7 F-Systems for fail-safe applications.