Thesis for the Degree of Master of Science


Year 2004
Nikolai Vatanski

Transforming control loop performance indices into economical values

A typical continuous industrial plant could have hundreds of control loops, which would compromise performance significantly according to recent research. Tuning causes poor performance. Usually, control loops are tuned to work optimally in specific process conditions only. They are tuned at start-up, after which tuning operators do not have a clear idea about the performance of control loops.

In the past decade, control loop performance assessment has been actively researched. The use of control loop performance measures in performance evaluation is a well-established practice. However, measures developed are often mathematical and interpretation requires background information. Hence, control loop performance measures have not been much used.

The aim of this thesis was to transform control loop performance measures into economical values to facilitate the interpretation of control loop performance measures.

The literary part of this thesis first introduces control loop performance measures and then elaborates on transforming methods found in literature and commercial software packages. It presents a general method to evaluate the economics of improved control.

The experimental part investigates the economic properties of control loop performance measures, using offline data from the Pyhäsalmi and Siilinjärvi concentrating plants.

Finally, the thesis proposes a strategy to analyze control loop economics using the control loop performance measures.

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