Contribution of analysis tools in preventive maintenance for the detection of defects related to safety instrumented systems to reduce industrial risks in a gas complex
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Date
2026
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Université Badji Mokhtar Annaba
Abstract
In the gas processing industry, Safety Instrumented Systems (SISs) are deemed as the most effective safety layer. These automated systems are designed to prevent major accidents from happening and if undesired event occurs, they minimizethe harm on people, environment and assets. However, their performance hinges on several factors including the chosen maintenance approach. This study contributes to the field of process safetyby focusing on how different maintenance strategies can optimize the performance of Safety Instrumented Systems (SISs). This thesis proposes a model using Stochastic Petri Net (SPN) to assess the performance of an existing Emergency Shutdown System (ESD) in a Flared Gases Recovery Unitat the Edjeleh field in southern Algeria. This research also analyzes the financial effect of proof tests, which can be significant, including direct costs (such as personnel, equipment, and logistics) and indirect costs (such as loss of production and gas flaring penalties). A
comprehensive strategy that optimizes proof test frequency and performs them during planned facility shutdowns can effectively manage and reduce these costs. The study's findings confirm that the proposed Stochastic Petri Net (SPN) model effectively evaluates how imperfect full and partial proof tests affect the average Probability of Failure on Demand (PFDavg) of Safety Instrumented Functions (SIFs). In addition, real-world application in an operational gas unit validates the proposed model's ability to optimize spare parts expenses through reliability analysis. This translates to significant cost savings without compromising the desired safety integrity levels (SILs), within two years, about 60% benefit has
been achieved comparing to the existing procurement process for the same timeframe. This research offers valuable insights for both the design phase of new EPC (Engineering, Procurement, and Construction) projects and the operation phase of existing facilities.
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Keywords
safety instrumented system; maintenance strategie; proof tests