Integrated Framework for Determining Safety Integrity Level for Improved Process Safety

Abstract

According to the recent trend for the integrated safety management of chemical plants as part of plant life cycle engineering, it is recommended that a safety integrity level (SIL) analysis be performed to simultaneously meet the operational efficiency and safety specifications of a process. In this paper, a unified framework is proposed for adapting life cycle engineering to risk assessment, including reusing the results, recommending a risk reduction by using a hazard and operability (HAZOP) support tool as a hazard identification method, and determining the SIL from a layer of protection analysis combined with fuzzy logic. First, a HAZOP support system is used to select scenarios with reducing efforts when the HAZOP study is implemented. Second, a fuzzy layer of protection analysis (fLOPA) is conducted to adjust the most reliable independent protection layer (IPL) by solving the objective uncertainty, which includes the failure rate data, probability of failure on demand, and subjective uncertainty. The required SIL for each scenario is determined, and a safety instrumented system is recommended to fit the demanded SIL. This framework, which is validated for a hydroxylamine case study, makes it possible to determine the required SIL with less effort and considers the uncertainties in the process, especially for plants that handle reactive and hazardous chemicals.