Achieved improvements in production lines
Improvements in grammage and moisture measurements
Grammage and moisture measurements can be improved by calibrating the sensors with traceable references and by eliminating detected errors. The measure reduces the uncertainty of these measurements by about 85%. This result is evident from the two publications below, which are based on improvements made to customers’ production lines. The articles contain data collected in production lines over ten years.
Improvements in grammage measurements
This article about improvements in grammage measurements has been published in ISA Transactions – magazine. The magazine publishes articles about best practices on industry.
Abstract. The automatic control of grammage (basis weight) in paper and board production is based upon on-line grammage measurement. Furthermore, the automatic control of other quality variables such as moisture, ash content and coat weight, may rely on the grammage measurement. The integrity of Kr-85 based on-line grammage measurement systems was studied, by performing basic calibrations with traceably calibrated plastic reference standards. The calibrations were performed according to the EN ISO/IEC 17025 standard, which is a requirement for calibration laboratories.
The observed relative measurement errors were 3.3% in the first time calibrations at the 95% confidence level. With the traceable basic calibration method, however, these errors can be reduced to under 0.5%, thus improving the integrity of on-line grammage measurements. Also a standardised algorithm, based on the experience from the performed calibrations, is proposed to ease the adjustment of the different grammage measurement systems. The calibration technique can basically be applied to all beta-radiation based grammage measurements.
Improvements in moisture measurements
This article about improvements of IR based moisture measurements has been published in Measurement – magazine. The magazine is published by international measurement organization IMEKO.
Improving the integrity of IR based online moisture measurement used in the paper and board industry, Measurement 44 (2011) 1937-1944 »
Abstract. The automatic control of product moisture content in the paper industry is based upon online moisture measurement. Furthermore, the automatic control of other quality variables such as coat weight may also rely on the moisture measurement. The integrity of infrared radiation (IR) based online moisture measurement systems was studied by performing basic calibrations at the mills with references sealed between two glass plates. The calibrations were performed according to the EN ISO/IEC 17025 standard which is a requirement for calibration laboratories.
The observed measurement errors were 2.9% moisture in the first time calibrations at the 95% confidence level. It is demonstrated that these errors can be reduced to under 0.5% moisture by applying traceable methods in the basic calibration, thus improving the integrity of online moisture measurements. Also a standardised algorithm, based on the experience from the performed calibrations, is proposed to ease the adjustment of different moisture measurement systems.
Improvements in grade-specific measurements
After calibration or tuning, preformed with references, the grammage and moisture measurements must still be calibrated for each product grade. We have developed a service for that purpose. We demonstrated that it is possible to reach a less than 0.5% uncertainty in grammage and 0.2% in moisture measurement. It is also possible to achieve an uncertainty of 0.5% in calculated dry grammage weight. The article has been published in Measurement – magazine.
Application of traceable sample area measurement in the calibration of online dry grammage measurement used in board production, Measurement 46 (2013) 1585-1591 »
Abstract. A method is described for the simultaneous calibration of online grammage and moisture measurement by applying machine reel sampling and traceable sample area measurement. The area measurement is based on a flatbed scanner and image analysis. It is demonstrated that a relative uncertainty of 0.5% can be achieved in dry grammage calibration at the 95% confidence level. The determination of grammage and moisture were performed by applying the EN ISO 536 and the EN ISO 287 standards, respectively. The described technique can also be applied with the calibrations performed for the paper industry.
Improvements in the traceability of dry grammage measurements
Improvements of grammage and moisture mesurements enhance the reliability of calculated dry grammage. Dry grammage equals to the amount of used dry raw materials in production. The better the raw material usage is known the better it can be controlled.
Below is a link to Aalto University’s dissertation. It’s about improving the metrological traceability of dry grammage measurement on a production line:
Improving the Metrological Traceability of Online Dry Grammage Measurement Used in the Paper Industry, Aalto University Doctoral Dissertations 207/2013 »
Abstract. 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.