Title: Optimal design of T² monitoring chart for chemical processes

Authors: Mohamed Bin Shams; Ali Elkamel; Krishna Moorthy; Golbahar Rafinejad; Aubhooti Saxena

Addresses: Department of Chemical Engineering, University of Bahrain, P.O. Box 32038, Isa Town, Kingdom of Bahrain ' Department of Chemical Engineering, University of Waterloo, Ontario, N2L 3G1, Canada ' Department of Chemical Engineering, University of Waterloo, Ontario, N2L 3G1, Canada ' Department of Chemical Engineering, University of Waterloo, Ontario, N2L 3G1, Canada ' Department of Chemical Engineering, University of Waterloo, Ontario, N2L 3G1, Canada

Abstract: In this paper, the optimal design of multivariate statistics-based monitoring charts for large scale systems is investigated. A cost function that explicitly accounts for the different quality monitoring costs is used to determine the parameters of the Hotelling's T² monitoring chart. The proposed approach is used to economically monitor the products in the Tennessee Eastman process (TEP). The implementation of a multivariate economical criterion in the design of the Hotelling's T² control chart provides an improved basis for the evaluation and repairs of out of control states and results in monitoring's cost minimisation through optimal sampling schedules. Due to the nature of the used economic model, the decision of switching from traditional statistical design to economic design requires the balance between the gained cost saving and the expected statistical performance of the T² monitoring chart. Finally, in order to evaluate the reliability of the estimated optimal parameters, a detailed sensitivity analysis is presented.

Keywords: multivariate statistics; Hotelling; T2 control charts; Tennessee Eastman process; TEP; optimisation; economic design; optimal design; control chart design; control charts; statistical process control; SPC; chemical processes; process monitoring; economic design; parameter reliability.

DOI: 10.1504/IJPSE.2015.075104

International Journal of Process Systems Engineering, 2015 Vol.3 No.4, pp.232 - 247

Received: 19 Jan 2015
Accepted: 19 Mar 2015
Published online: 03 Mar 2016 *

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