Evidence Before Optimization: Maintenance Prioritization by Evidence Sufficiency in Compressed-Air Systems

Limited diagnostic resources require maintenance tasks to be prioritized. Under compensatory multi-criteria decision analysis (MCDA) alone, a machine with larger flow-based criterion values can outrank one for which the available evidence prescribes a different action. This study couples a previously developed evidence-sufficiency procedure with compensatory prioritization through a lexicographic rule. The D-code fixes the admissible action for each machine, and MCDA ranks only tasks of the same type. In eight short machine-level records from one plant, the MCDA-only order places two D2 tasks ahead of the single D4 diagnostic task, which the two-stage order places first. This conflict persists at all 256 combinations of the interval bounds of the flow-based criteria. A retrospective ultrasonic survey localized 12 static leaks on four machines. In a retrospective replay with a common localization modality, the two-stage order covers less at one visit, 33.3% versus 41.7% of the leaks and 23.0% versus 50.8% of the semi-quantitative estimated equivalent flow. At two visits, it covers 75.0% versus 50.0% and 73.8% versus 68.5%. At nominal inputs, the selected sets coincide at three and four visits. Within D2, MCDA did not outperform a flow-only ranking. Within the proposed framework, the admissible action is established before compensatory prioritization.