An Introduction to Normal-Operating-Zones for Process Monitoring

Process monitoring plays a major role in ensuring the safety and efficiency of industrial processes. This paper introduces a new concept of normal operating zones for process monitoring. The normal operating zone (NOZ) is a high-dimensional geometric space consisting of variation ranges of multiple related process variables in normal conditions. It provides spatial information among process variables, as an indispensable complement to time information provided by time series of process variables. Abnormality detection and operation guidance for improved efficiency can be realized for multivariate processes by integrating time and spatial information in a visual and transparent way. Experimental and industrial case studies are provided to illustrate the applications of NOZs on threetank systems and power generation units.