I am trying to wrap my head around some excerpts from:
- CCPS Layer of Protection Analysis
- CCPS Guidelines for Independent Protection Layers and Initiating Events
- IEC 61511
I am trying to understand how to apply Approach B and use two functions in the BPCS (e.g. a control loop and an alarm) as independent Protection Layers (IPLs) in a LOPA, when the CPU is shared.Guidelines are very vague about it.
What parameters should be looked at, to decide to apply Approach B?
Note: I understand that, if the guidelines are not clear to me, I should not apply Approach B. The request comes from a client who is trying to consider as many safeguards as possible before having to update their BPCS and SIS.