A METHODOLOGY FOR FAULT-DIAGNOSIS IN LARGE CHEMICAL PROCESSES AND AN APPLICATION TO A MULTISTAGE FLASH DESALINATION PROCESS - PART II

In Part I, an efficient method for identifying faults in large process es was presented. The whole plant is divided into sectors by using str uctural, functional, or causal decomposition. A signed directed graph (SDG) is the model used for each sector. The SDG represents interactio ns among process variables. This qualitative model is used to carry ou t qualitative simulation for all possible faults. The output of this s tep is information about the process behaviour. This information is us ed to build rules. When a symptom is detected in one sector, its rules are evaluated using on-line data and fuzzy logic to yield the diagnos is. In this paper the proposed methodology is applied to a multiple st age flash (MSF) desalination process. This process is composed of sequ ential flash chambers. It was designed for a pilot plant that produces drinkable water for a community in Argentina; that is, it is a real c ase. Due to the large number of variables, recycles, phase changes, et c., this process is a good challenge for the proposed diagnosis method . (C) 1998 Elsevier Science Limited.