PRODIAG: A process-independent transient diagnostic system - I: Theoretical concepts

A novel first-principles-based diagnostic system called PRODIAG is proposed for on-line detection and identification of faulty components during incip ient off-normal process conditions. The concepts of qualitative physics rea soning and function-oriented diagnostics are employed in the design of PROD IAG and result in two unique capabilities not found in other plant-level di agnostic systems. First, PRODIAG is fully portable as it requires only modi fication of the input files containing the appropriate process schematics i nformation to be able to diagnose single-component failures in different pr ocesses/plants. Second, PRODIAG detects unanticipated faults. Hence, it doe s not require the prespecification and formulation of rules to cover every conceivable fault scenario, and unlike traditional approaches, it is nor li kely to misdiagnose unforeseen events. PRODIAG's approach is to map process symptoms Into component faults through a three-step mapping procedure with a knowledge base containing three distinct types of information: qualitati ve macroscopic balance equation rules, functional classification of process components, and the process piping and instrumentation diagram. The concep ts introduced in the proposed diagnostic system are described, and an illus trative example shows how they are used in plant-level diagnostics.