A Systematic Causality-Based Model for Risk Assessment and Management of Change in Chemical Plant Lifecycle

The lifecycle of a chemical plant includes development, design, construction, operation, maintenance, and decommissioning phases. When changes are proposed, primarily during the operation and maintenance phases, risk assessments are conducted to evaluate both implementing and not implementing the changes. When implementing a change leads to risk reduction, the process returns to the development and/or design phases for redevelopment and/or redesign. Among the risk assessment methods, HAZOP is widely used. When modifications qualify as Replacement In Kind (RIK), redevelopment and/or redesign efforts are reduced, making RIK determination essential. On the other hand, the business process model (BPM) structures engineering activities and information flows but lacks an explicit design rationale representation. This study proposes a systematic causality-based model to systematically represent the design rationale, aiding a logical and efficient RIK determination. A case study examined risk assessment, focusing on reactor minimum flow conditions and their impact on a downstream distillation column. The proposed model identified potential hazards and was cross-referenced with HAZOP results, confirming comprehensive identification of key examination points, including control system considerations beyond HAZOP’s scope. Therefore, the proposed model enhances the consistency between PHA results and design rationale, ensuring a structured and transparent approach to change management.