Browsing by Author "Ikonen, Erkki, Prof., Aalto University, Metrology Research Institute, Finland"

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Improving the Metrological Traceability of Online Dry Grammage Measurement Used in the Paper Industry
(2013) Kangasrääsiö, Juha
School of Electrical Engineering | Doctoral dissertation (article-based)
In the paper industry, the automatic control of raw material consumption and product quality relies upon online grammage (total mass per unit product area) and moisture measurement. The optimisation of raw material consumption is vital to the profitability of production, and the even quality is essential for satisfying customer needs. It was shown in this work that the basic errors of radioisotope Kr-85 based grammage and IR based moisture measurements, which are commonly used in the paper industry, can be decreased on average approximately 85% with traceable calibration methods. Moreover, a novel method was created for the simultaneous grade specific calibration of these measurements by applying machine reel sampling and traceable sample area measurement. It was demonstrated that a relative uncertainty of 0.5%, at the 95% confidence level, can be achieved in dry grammage calibration. The calibrations were performed according the EN ISO 536 (grammage) and the EN ISO 287 (moisture) standards. The uncertainties of existing measurement systems can be reduced usually over 50% with the created methods. The decrease of measurement uncertainty offers an opportunity for significant economic savings since one per cent change in the dry raw material consumption of a typical production line affects several hundreds of thousands euros in the annual raw material costs. The presented calibration methods can basically be applied to all paper and board production lines.