Frequently Asked Question
We are performing a SIL Verification for an existing plant (plant has 20 years). What Mission Time do we need to choose? If it was a new plant, we would usually take 25 years, and the PDF calculations would start "from now". How can we consider that we ar
Last Updated 5 years ago
The calculation takes the Probability of Failure on Demand over the Mission Time and averages it. Since the probability of failure increases overtime, the longer the Mission Time, the higher the PFD Average. If you were to assume half of the Mission Time, your results would be incorrect. You should input the full Mission Time into the calculation, even if you are half way through it. Remember that the calculation also assumes at the end of the Mission Time all SIF equipment is replaced or refurbished.