Mass Concentration
Ratios of dry material to liquid in a slurry determine the mechanical requirements for pumping and screening in a mill. Standard laboratory tests define consistency percentage as the dry weight of solids expressed as a fraction of the total weight of the aqueous suspension. Proper control of this value ensures that the chemical treatments applied to the pulp interact effectively with the cellulose surfaces.
It governs the density of the stock as it moves from the pulper toward the headbox.
Flow Regulation
Variations in water volume alter the shear forces required to move the pulp through the pipework. When consistency percentage rises above four percent, the suspension becomes a non-Newtonian fluid that resists flow and demands higher energy inputs from the pumps. Low concentrations facilitate the removal of heavy contaminants through centrifugal cleaners.
This balance dictates the sizing of storage chests and the capacity of the white water system.
Operational Constraint
Accuracy in measurement prevents the over-application or under-application of sizing agents and dyes. If the consistency percentage fluctuates during the formation of the sheet, the basis weight of the paper will vary across the web. Modern sensors provide real time data to automated valves to maintain the stability of the stock.
