Finding a trade-off between observability and economics in the fault detection of chemical processes

This paper presents a methodology to quantitatively gauge the potential economical loss due to unobserved faults when standard statistical monitoring charts are used. It is shown that in closed loop operation, a shorter time for detection may result from retuning the controller at the expense of higher product variability. Accordingly, an optimization approach is proposed for finding a trade-off between the economic losses resulting from lack of detection and losses resulting from higher product variability. In order to account for faults with different frequency contents, the method is applied in the frequency domain. The proposed optimization based methodology is later validated in the time domain.