Proceedings of the

The 33rd European Safety and Reliability Conference (ESREL 2023)
3 – 8 September 2023, Southampton, UK

Key Performance Indicators of Aging Safety Barriers in Oil and Gas Facilities

Stefano Marchetti1,a, Francesco Di Maio1,b, Enrico Zio1,2,c,d, Luca Decarli3,e, Laura La Rosa3,f and Giuseppe Nicotra3,g

1Energy Department, Politecnico di Milano, Milano 20156, Italy.

2MINES Paris-PSL, Centre de Recherche sur les Risques et les Crises (CRC), Sophia Antipolis, France.

3Eni Natural Resources - HSEQ, via Emilia 1, 20097 San Donato Milanese, Italy.


Aging of safety barriers can degrade their performance and increase risk in Oil and Gas (O&G) facilities. Condition-informed risk assessment can be used to assess the risk of a facility given the actual performance of its safety barriers and eventually prescribe maintenance activities. In this work, we propose a novel definition of Key Performance Indicators (KPIs) of safety barriers that allows accounting for their aging. When sufficient barrier failure data are available, a Q-Weibull model is used to quantify a corrective factor that multiplies the no-aging basis KPI value. When barrier failure data are scarce, which is often the case in practice, the corrective factor is quantified by an expert-based Weibull-like distribution, that anchors some or all the different stages of barrier life (such as infant and wear-out mortality phases) with the few, limited data available. The safety barrier of Design Integrity (DI), typically employed in upstream Oil and Gas (O&G) platforms, is numerically elaborated as a practical example.

Keywords: Safety barrier, Aging, Key Performance Indicator (KPI), Bathtub curve, Q-Weibull distribution, Maximum Likelihood Estimation (MLE).

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