An Integrated Approach to Safety Instrumented System Lifecycle Management: Risk Evaluation and Optimization in the Petrochemical Industry Using Genetic Algorithms
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Date
2025-02-28
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Instrumentation Mesure Métrologie Vol. 24, No. 1, February, 2025, pp. 23-34
Abstract
This study aims to present a complete methodology that integrates evaluation and
optimization to address the entire Safety Instrumented Systems (SIS) lifecycle. A
comprehensive methodology for SIS evaluation and optimization is proposed, specifically
targeting a system, called I-1165, responding to a high-high level alarm in a De-ethanizer
Reflux Drum V-2, which is used to separate ethane and lighter components from heavier
hydrocarbons. The methodology begins with a comprehensive HAZOP study to identify
and assess potential risks, which are then estimated using PHAST software. SIL allocation
is performed using the LOPA method, followed by the determination of Achieved SIL
through analytical formulas. The Achieved SIL is iteratively validated by comparing it
with the Required SIL. If the Achieved SIL does not meet the required standards, a genetic
algorithm (GA) is employed to optimize the SIS design and maintenance strategies. This
process continues until the target SIL is achieved, or an alternative architecture is
proposed, ensuring that the SIS performance aligns with safety requirements. Optimization
results for the I-1165 system reveal a significant improvement in PFDAvg from 2.1E-2 to
6.10537E-4, meeting and exceeding the required SIL 2 performance. This improvement
not only enhances system safety and reliability but also ensures compliance with IEC
61508 standards while reducing lifecycle costs by optimizing the frequency of
maintenance and testing intervals.