This paper deals with detection of faults in the Tennessee Eastman problems (TEP) that have been found unobservable by previous studies. Hotelling’s T
2 charting based on the cumulative sums of the faults’ relevant variables was successful in detecting these faults, however, with significant delays. To reduce these delays, it is proposed to retune the feedback controllers involving controlled and manipulated variables used for detection. An optimization-based methodology that searches for an optimal trade-off between fault detection and control performance is formulated. The resulting controller design is compared with a design previously reported in the literature showing that significant reductions in the detection delays and overall reductions in the plant’s costs can be achieved by proper tuning of controllers. Both individual and simultaneous occurrence of faults is considered. Although the proposed method was illustrated using TEP process, the approach is general and can be applied to other processes.