The influence of bar width on bar forces and fibre shortening in low consistency pulp refining

Abstract

This paper describes forces in pulp refiners and their influence on fibre shortening. We show that force per bar length obtained by a simple calculation from the Specific Edge Load (SEL) is a useful parameter to describe threshold force levels below which levels of fibre cutting can be avoided. Our analysis is supported by data from studies on four refiners and in one case by direct measurement of force in an operating refiner. In particular, we show that small bar widths lead to large forces and consequently that SEL must be adjusted to lower levels to avoid fibre cutting. We also speculate on the lower limits of bar width.