One of the fundamentals of the Probability of Failure on Demand (PFDavg) calculations in SIL verification analysis, is the concept of a constant failure-rate during useful life of the equipment. Probabilistic calculations assume that the failure rate of the devices used in a Safety Instrumented System (SIS)…
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Entries tagged with: Steve Gandy
- by Steve Gandy, CFSP
- Thursday, June 22, 2017
- Functional Safety
Why Run-to-Fail Is Not A Good Maintenance Strategy For SIS
- by Steve Gandy, CFSP
- Tuesday, March 30, 2021
- Functional Safety
Why Sharing Components Between SIS & BPCS Is Not A Good Idea
This is a topic which comes up time and again, especially when reviewing legacy systems. Although IEC61511 doesn’t preclude the use of shared devices, it does however provide guidance under Clause 11 of what the constraints are. Even though the Safety Instrumented System (SIS) and Basic Process Control System (BPCS)…
