A fuzzy logic model of deionised and water for injection systems for sizing and capacity assessment under uncertainty

The operating performance of deionized and water for injection (DI/WFI) distribution systems can be difficult to analyse due to the highly variable demand that is drawn from these systems, a situation compounded by schedule uncertainties. This paper presents a fuzzy logic (FL) model of a typical DI/WFI system simulating schedule uncertainties in the opening and closing events of the offtake valves based on operator behaviour, e.g. tiredness of the operators. The model utilises discrete-event simulation to calculate the demand profile of the distribution system and a continuous simulation to compute the variation of the level in the storage tank. It is shown that the FL model may be useful in the design of new DI/WFI systems if little historical data are available.