(52bb) Using IE and IPL Failure Rates to Establish Initial Inspection Intervals, and Maximum Out of Service Time, and Deferral Time Limits for Critical Process Safety Features
AIChE Spring Meeting and Global Congress on Process Safety
2022
2022 Spring Meeting and 18th Global Congress on Process Safety Proceedings
Global Congress on Process Safety
GCPS - Process Safety Poster Session
Monday, April 11, 2022 - 5:00pm to 7:00pm
This paper presents a standardized approach for determining the maximum time allowable for bypasses and deferrals, based on when the initiating frequency or the probability of failure on demand changes enough to make a statistically significant change to the stated IEF or PFD of the IE or IPL respectively. Bypasses and deferrals should of course be strongly discouraged as a matter of operational discipline and to foster good process safety culture, but the approach in this paper serves to reduce the uncertainty in the risk judgements of what is the maximum time allowable for a bypass or deferral before a statistically significant change in the risk of the scenario occurs. This can in turn reduce the number or or time spent the related risk assessments (miniture PHAs) for an associated Management of Change.