Human Factors in Process Safety: Practical Application in Safety Instrumented Functions

Safety Instrumented Functions (SIF) are critical for ensuring process safety in industries such as oil and gas. While IEC 61511-1:20161 acknowledges the role of human actions within SIF, reliability assessments often overlook the human error component. Historical incidents, including BP Deepwater Horizon2 and Fukushima3, underscore the significant impact of human factors. In addition to this context, Human Reliability Analysis (HRA) has gained prominence in Brazil, considering the recent updates on operational safety regulatory framework4. This study integrates Petro-HRA5,6 with traditional Safety Integrity Level (SIL) analysis to evaluate the influence of human actions on SIF reliability. The methodology follows five key steps: scenario definition, critical task analysis, tabular task analysis, quantification and representation of human error. The focus is on operator actions during the selection of the operational mode of Water-Alternating-Gas (WAG) injection wells, where human failure could compromise SIF availability. By applying a Fault Tree Analysis (FTA), the study quantifies the impact of human errors on SIF performance. Results demonstrate that accounting for human error significantly influences SIF reliability, while implementing targeted Error Reduction Measures (ERM) enhances system safety, reinforcing the need to integrate human factors into safety assessments.