Optimizing turnaround maintenance execution : a unified framework for constraint management and simops control – a case study in a Thai petrochemical plant

Abstract

Turnaround Maintenance (TAM) is vital for petrochemical plant reliability and safety; however, shutdown execution is high-risk, resource-intensive, and frequently subject to schedule overruns. Area supervisors must manage emergent work, delays, and overlapping tasks while complying with strict safety governance. Conventional control methods such as CPM and PERT provide baseline logic but lack the short-cycle adaptability and field-level decision support required in dense, fast-moving execution environments. This study develops and evaluates an execution-control framework to strengthen agility and execution reliability during TAM. The framework integrates a 24-hour look-ahead product backlog, shift-tempo daily scrums, and a live customised SIMOPS matrix with standard project controls to provide near-term visibility, structured communication, and guardrails for safe concurrency. A pull-planning workshop, adapted from Last Planner System (LPS) principles, is embedded in detailed planning to surface constraints, secure resource commitments, and establish milestone targets, thereby bridging planning and execution. The framework was evaluated through (i) a workshop-based simulation comparing conventional and framework-enabled decision-making across predefined disruption scenarios, and (ii) a live case study conducted during an annual petrochemical unit shutdown. The simulation indicated improved decision quality without increasing decision time. In the live case, the baseline schedule was shortened, emergent delays were largely absorbed, and downstream tasks were effectively resequenced to reduce standby losses. The study demonstrates that LPS-derived execution practices, when adapted to shift tempo and integrated with a customised SIMOPS matrix and Scrum-based backlog, can provide a practical execution-control mechanism for TAM. Importantly, supervisors reported higher confidence and clearer schedule control, while communication clarity improved; however, response time remained constrained by safety governance requirements. Further research should refine escalation triggers and explore digital, real-time support to enhance responsiveness during execution.