Computer-aided Operability Study

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In this research, an object-oriented approach for computer-aided HAZOP has been developed by collaboration with VTT Automation in Finland from 1997 to 1999.The HAZOP System consists basically of the knowledge bases (the plant sepcific knowledge base, the generic knowledge base ) and the inference engine. The generic knowledge in the HAZOP System consists of components malfunction models and suggested action knowledge. Causal relationships between variable deviations and failure modes for components are modeled as component malfunction models in the HAZOP System. Actions required are divided into actions for the cause and actions for the consequence. Knowledge of actions for the cause and the consequence consist of prevention and detection, mitigation and detection respectively. This knowledge is developed in a process-independent manner and is applicable to wide variety of process flow sheets.The plant specific knowledge consists of information about materials, reactions, and the plant structure (P and IDs). The plant specific knowledge varies from plant to plant and has to be provided by the user. The user interacts with the system through the graphical user interface. The user can easily draw the P and IDs of the process arranging component icons in the HAZOP System graphical editor. Once the P and IDs is input into the system, the corresponding component malfunction gets connected automatically internally in the appropriate manner.HAZOP analysis is initiated by specifying a process variable deviation in a process unit or pipeline in the P and IDs. Each process variable of equipment is studied in sequence by searching the knowledge base, using key words to describe deviations.The HAZOP System for this work is implemented in an object-oriented architecture using expert system shell G2.