The relation between net power, gap, and forces on bars in low consistency refining

The objective of this study is to experimentally investigate the relationships between local bar forces, plate gap and fiber length in a single-disc low consistency refiner. Piezoelectric sensors are used to measure normal and shear forces applied to pulp fibers by the refiner bars. It is shown that there is a non-linear relationship between measured bar forces and length-weighted fiber length that mirrors the established relationship between length-weighted fiber length and the inverse of plate gap. As the plate gap is reduced, the length-weighted fiber length remains relatively constant while net refiner power and the mean peak normal and shear forces increase. These trends continue up to a threshold values of mean peak normal and shear forces of approximately 8 N and 2.4 N, respectively. Above this threshold, mean peak normal and shear forces continue to increase but the length-weighted fiber length exhibits negative linear relationships with these forces. These results can be used as the initial study for onset detection of fiber cutting and that these sensors have promising potential to be used as the basis for advanced refiner control strategies.