STPA-FTA hybrid hazard analysis framework applied to a high integrity pressure protection system
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Date
2026-03-26
Journal Title
Journal ISSN
Volume Title
Publisher
Life Cycle Reliability and Safety Engineering.Springer Nature.
Abstract
The increasing complexity of petrochemical systems demands innovative hazard analysis methods capable of capturing
both component and systemic failures. In this paper, we propose a new hazard analysis framework that integrates SystemTheoretic Process Analysis (STPA) with traditional Fault Tree Analysis (FTA). Initially, STPA is applied to identify Unsafe
Control Actions (UCAs) and associated loss scenarios. Subsequently, FTA is employed to model dysfunctional component
behaviors and quantify critical risk metrics, including the Probability of Failure on Demand (PFDavg), Minimal Cut Sets
(MCSs), and Safety Integrity Level (SIL) using GRIF software. Finally, STPA outputs are incorporated into the traditional
FTA by treating UCAs as basic developed events. The framework is applied to a High Integrity Pressure Protection System (HIPPS 2351) safeguarding the C-63 distillation column at the Skikda RA1K refinery. The results revealed additional
MCSs that were not discovered by the traditional FTA, which increased the number of MCSs from 8 to 39. Furthermore,
the Birnbaum Importance Factor is applied to rank and prioritize UCAs, identifying the most critical UCAs (UCA 1
through UCA-15) that have a significant impact on the HIPPS 2351 reliability. Overall, the proposed framework provides
a comprehensive hazard analysis covering both qualitative and quantitative aspects.