General purpose logic solvers for safety applications

3 General-purpose logic solvers for safety applications 

The application of PLCs to the process sectors required that the owner/operator understand the PLC dangerous failure modes and their frequency, methods to mitigate these problems, and proper testing to recognize undetected dangerous failure modes. This situation required a close working relationship between the owner/operator and the manufacturer. Those manufacturers who were capable of providing support in this effort have survived the hectic crowded PLC market of the 70s and 80s. 

When configuring a general-purpose logic solver for SIS applications, consider the following  

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Determine whether the logic solver manufacturer can supply safety components (e.g., fail-safe outputs) and use these to the extent possible. 

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