Interpretation of force profiles in mill-scale LC refining

Abstract 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 individualbar 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 assingle peakevents which feature one peak corresponding to thefiber compression forceand asdual peakevents corresponding to fiber compression force and thecorner force. The bar passing events are then analysed based on theirmean force profilesand theirdual peak ratioin 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.