Risk-Informed Systems Engineering Framework for the Design and Reliability Validation of an Onboard Vacuum Drying System

The increasing adoption of exhaust gas cleaning systems (EGCSs) in the maritime industry has raised concerns regarding the management of sludge residues generated during wet scrubber operation. Conventional onboard sludge handling methods primarily rely on temporary storage and onshore disposal, resulting in increased storage requirements, disposal costs, and environmental burdens. Although vacuum drying has emerged as a promising approach for onboard sludge volume reduction, limited studies have addressed the integrated risk-informed design, reliability evaluation, and operational validation of onboard vacuum drying systems under marine operating conditions. This study proposes a risk-informed systems engineering framework for the design, reliability evaluation, and validation of an onboard vacuum drying system (VDS) for EGCS sludge treatment. The framework establishes a closed-loop process in which functional analysis and hazard identification inform quantitative reliability assessment and structural verification, which in turn drive design refinement and are subsequently confirmed through hardware-in-the-loop (HIL) validation and experimental testing. The results demonstrated stable vacuum operation at the designated pressure of 3 Torr for more than 30 min, with a minimum chamber pressure of 0.08 Torr. Structural assessment confirmed that the calculated stresses remained well below the allowable limits of ASME Section VIII Division 1, while modal analysis indicated acceptable dynamic stability. FMECA-based design refinement reduced the Risk Priority Number (RPN) values of major components by 50–67%, with an average reduction of 53.3%. HIL-based validation and experimental testing further verified the effectiveness of the control architecture and the operational feasibility of the system. The study demonstrates how a risk-informed systems engineering framework can systematically integrate structural verification, quantitative reliability improvement, and operational validation for onboard environmental treatment systems. The proposed framework provides a practical and transferable methodology for enhancing the safety, reliability, and operational feasibility of marine systems operating under complex onboard conditions.