Failure Probability Is it very important to calculate very precisely the average probability of failure “PFDavg” of a Safety Instrumented Function? The short answer is “NO“, and we will try to explain it below. The first thing to say is that Functional Safety is much more than meeting the probability of failure. IEC 61511 defines …
Complex Architectures in the final element (I) Calculating the probability of failure (PFDavg) in a complex architecture is not usually easy, especially if we do not know the concepts well. Let’s see in this case a complex architecture in the final element. Example: Logic 4oo4 in the final element From time to time we find …
Partial Valve Stroke Test (PVST) The Partial Valve Stroke Test is used in the Safety Instrumented Function (SIF) to diagnose valve failures without having to stop the process. The problem of the shut-off valves in low demand SIFs is that they remain in a position (open or closed) for many months, without knowing if they …
