Studying the Relationship between Inherently Safer Design and Equipment Reliability
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During the last decade, inherent safety has emerged as an area of interest in both academic and industrial research. Various regulatory bodies (including US environment protection agency) have enforced the consideration of inherently safer design alternatives. This enforcement, however, may not serve the purpose of reducing the frequency of process incidents due to the drawbacks such as risk migration associated with inherent design philosophy. This study focuses on analyzing the relationship between inherent safety and reliability as chemical project proceeds from initial to later stages of design. The main objective of this research is to evaluate the possibility of risk escalation caused due to lowering of system reliability during implementation of inherent safety principles applied with an objective to lower the consequence element of risk. This lowering of system reliability can increase the likelihood of a process incident, thus resulting in an increased risk, ultimately defeating the purpose of applying the inherent design philosophy. The developed methodology involves quantifying inherent safety based on the design stage under consideration using a quantification technique that utilizes process data available during that stage of design. This is followed by determining reliability and availability of the system using reliability databases or static reliability modeling for various design alternatives considered during that design stage. Lastly, the trend observed between quantified inherent safety and reliability/availability is used to determine the required relationship. The application of the developed methodology to process selection stage, conceptual stage, and detailed engineering stage reveals that the relationship between inherent safety and reliability (and availability) is complicated and varies as per the design stage under consideration. Thus, an important conclusion that can be drawn from this research is that an inherently safer design may not be associated with higher system reliability and lower risk. Lastly, the developed methodology is validated for the case study of T2 Laboratories explosion and fire. An important observation from these case studies is the ineffectiveness of quantified inherent safety in terms of Dow F&EI to capture the severity of situation revealed by detailed reliability analysis.
Ade, Nilesh (2017). Studying the Relationship between Inherently Safer Design and Equipment Reliability. Master's thesis, Texas A & M University. Available electronically from