Skip to content
Accessible Unlicensed Requires Authentication Published online by De Gruyter October 23, 2021

Interpretation of force profiles in mill-scale LC refining

Matthias Aigner, James Olson, Yu Sun and Peter Wild


A set of piezo electric force sensors is implemented in a 52-inch mill-scale low consistency refiner to explore the effect of varying operating conditions on bar force profiles. The sensor replaces a short length of a stator bar and measures normal and shear forces applied during the passage of each rotor bar. In previous work with this type of force sensor a rotary encoder was used to investigate force profiles for individual bar passing events (BPE) on a 16-inch laboratory-scale refiner. In the work presented here, force profiles for individual BPEs are identified based on key features in the time domain force data. The individual bar force profiles are classified as single peak events which feature one peak corresponding to the fiber compression force and as dual peak events corresponding to fiber compression force and the corner force. The bar passing events are then analysed based on their mean force profiles and their dual peak ratio in the bar passing event. Findings are compared and validated by previous work on bar force profiles. It is shown that dual peak events which are considered to represent the corner force, are present through out the whole range of refining and increase with increased refining energy. This increases the understanding of the way corner force contributes to the refining process. Furthermore, it is found that different radial positions on the stator plate are subjected to different force profiles. This is thought to be due to the difference in tangential speed and a change in the fiber and floc material properties at different radial positions.

Funding source: Canadian Network for Research and Innovation in Machining Technology, Natural Sciences and Engineering Research Council of Canada

Award Identifier / Grant number: 11R1977

Funding statement: This work is funded by a Collaborative Research and Development Grant provided by the Natural Sciences and Engineering Research Council of Canada (NSERC, Grant No. 11R1977) and the following partners, who we thank for their ongoing support: AB Enzymes, Alberta Newsprint Company, Andritz, BC Hydro, Canfor, Catalyst Paper, FPInnovations, Holmen Paper, Meadow Lake Pulp (Paper Excellence), Millar Western, NORPAC, West Fraser, Westcan Engineering, and Winstone Pulp International.


The authors gratefully acknowledge the assistance of Chad Toth, Pat Cooper and their colleagues at the Catalyst Paper Excellence mill at Crofton BC during the preparation for and execution of the refining trials.

  1. Conflict of interest: The authors declare no conflicts of interest.


Aigner, M., Olson, J., Wild, P. (2020) Measurement and interpretation of spatially registered bar-forces in LC refining. Nord. Pulp Pap. Res. J. 35(4):600–610. doi: 10.1515/npprj-2020-0064.Search in Google Scholar

Batchelor, W.J., et al. (1997) Forces on fibres in low consistency refining: Shear Force. J. Pulp Pap. Sci. 23(1):11–18.Search in Google Scholar

Elahimehr, A. (2014) Low Consistency Refining of Mechanical Pulp: The Relationship Between Plate Pattern, Operational Variables and Pulp Properties, Ph. D. Thesis. doi: 10.14288/1.0135584.Search in Google Scholar

Eriksen, O., et al. (2008) Fibre floc drainage – a possible cause for substantial pressure peaks in low-consistency refiners. Nord. Pulp Pap. Res. J. 23(3):321–326.10.3183/npprj-2008-23-03-p321-326Search in Google Scholar

Eriksen, O., Gregersen, Ø., Krogstad, P.-Å. (2007) Refining zone pressure in a mill-scale TMP refiner measured by fibre-optic sensors. Nord. Pulp Pap. Res. J. 20(4):468–476. doi: 10.3183/npprj-2005-20-04-p468-476.Search in Google Scholar

Harirforoush, R., Olson, J., Wild, P. (2017) In-process detection of fiber cutting in low consistency refining based on measurement of forces on refiner bars. Tappi J. 16(4):460–469.Search in Google Scholar

Harirforoush, R., Olson, J., Wild, P. (2018) Indications of the onset of fiber cutting in low consistency refining using a refiner force sensor: The effect of pulp furnish. Nord. Pulp Pap. Res. J. 33(1):58–68. doi: 10.1515/npprj-2018-3013.Search in Google Scholar

Harirforoush, R., Wild, P., Olson, J. (2016) The relation between net power, gap, and forces on bars in low consistency refining. Nord. Pulp Pap. Res. J. 31(1):71–78. doi: 10.3183/NPPRJ-2016-31-01-p071-078.Search in Google Scholar

Kappel, J. Mechanical Pulps: From Wood to Bleached Pulp. Tappi Press, Atlanta, GA, 1999.Search in Google Scholar

Kerekes, R.J. (2011) Force-based characterization of refining intensity. Nord. Pulp Pap. Res. J. 26(01):014–020. doi: 10.3183/NPPRJ-2011-26-01-p014-020.Search in Google Scholar

Kerekes, R.J., Meltzer, F.P. (2018) The influence of bar width on bar forces and fibre shortening in low consistency pulp refining. Nord. Pulp Pap. Res. J. 33(May):1–13. doi: 10.1515/npprj-2018-3028.Search in Google Scholar

Kerekes, R.J., Schell, C.J. (1992) Characterization of fibre flocculation regimes by a crowding factor. J. Pulp Pap. Sci. 18(1):32–38.Search in Google Scholar

Kerekes, R.J., Senger, J.J. (2006) Characterizing refining action in low-consistency refiners by forces on fibres. J. Pulp Pap. Sci. 32(1):1-–8. Available at: in Google Scholar

Llobera, M. (2001) Building past landscape perception with GIS: Understanding topographic prominence. J. Archaeol. Sci. 28(9):1005–1014. doi: 10.1006/jasc.2001.0720.Search in Google Scholar

Lundin, T., Batchelor, W., Fardim, P. (2009) Fiber trapping in low-consistency refining: New parameters to describe the refining process. Tappi J. 8(July):15–21.Search in Google Scholar

Luukkonen, A. Development of a methodology to optimize low consistency refining of mechanical pulp, Ph. D. Thesis. University of British Columbia, 2007.Search in Google Scholar

Martinez, D.M., Kerekes, R.J. (1994) Forces on bars in low consistency refining. Tappi Journal 77(12):119–123.Search in Google Scholar

Miller, M., Luukkonen, A., Olson, J.A. (2017) Effect of LC refining intensity on fractionated and unfractionated mechanical pulp. Nord. Pulp Pap. Res. J. 32(3):386–394.10.3183/npprj-2017-32-03-p386-394Search in Google Scholar

Olender, D., Wild, P., Byrnes, P. (2008) A piezoelectric forces sensor for mill-scale chip refiners. Proc. Inst. Mech. Eng., E J. Process Mech. Eng. 222(2):115–122. doi: 10.1243/09544089JPME172.Search in Google Scholar

Olson, J.A., et al. (2003) Characterizing fibre shortening in low-consistency refining using a comminution model. Powder Technol. 129(1–3):122–129. doi: 10.1016/S0032-5910(02)00129-8.Search in Google Scholar

Prairie, B., et al. (2007) Forces during bar-passing events in low consistency refining: Effects of refiner tram. Pulp Pap. Can. 108(9):34–37. doi: 07A1123062.Search in Google Scholar

Prairie, B.C. (2005) Measurement of Forces in a Low Consistency Refiner, M. Sc. Thesis. doi: 10.1016/j.jmaa.2012. in Google Scholar

Received: 2021-09-02
Accepted: 2021-09-25
Published Online: 2021-10-23

© 2021 Walter de Gruyter GmbH, Berlin/Boston