Fibre Fraction
Hydro-pulping operations measure the coarse screen reject fraction to control the mass ratio of oversized contaminants separated from the accepted stock during primary stock preparation. Mills regulate this hydraulic parameter by adjusting basket hole diameters and rotor tip speeds to protect downstream refining equipment from abrasive particles. Heavy mineral debris and dense plastic fragments accumulate inside the reject stream, leaving clean cellulose fibers to pass through the perforated cylinder toward the paper machine wet end.
Operators monitor daily discharge consistency because excessive fiber loss degrades final board strength and lowers overall economic yield. Reject removal efficiency relies upon proper pressure drops across the screening zone, maintaining stable hydrodynamic shear forces without binding the aperture openings. Excessive reject rates indicate worn cylinder plates or incorrect dilution water flows, forcing mills to replace hardware components before production suffers.
Process Efficiency
Stock preparation lines require precise control over reject removal because unrefined bundles disrupt formation uniformity on high speed cylinder formers. Heavy contaminants such as hot melt adhesives and wet strength fragments collect within the heavy fraction loop, demanding continuous clearance to prevent plugging. Mechanical technicians inspect rotor clearances weekly because minor shifts alter velocity profiles along the screening surface.
Closing loop configurations return secondary accepts back to the main hydrapulper, reclaiming trapped fibers while concentrating inert debris for municipal disposal. Proper hydraulic balancing reduces energy consumption per ton of finished linerboard, lowering operating expenditures across the entire preparation department.
Quality Tolerance
Converting plants demand clean containerboard free from embedded debris that causes die cutting interruptions and blade wear during corrugated box manufacturing. Strict mill standards limit foreign inclusion counts per square meter of finished substrate to protect expensive printing cylinders and creasing rules. Excess contaminant levels compromise internal bond strength and reduce compression resistance values required for heavy duty shipping containers.
Quality control laboratories test dried handsheets regularly to verify that screening procedures remove extraneous material without damaging individual cellulose fibers. Finished print stock must display uniform ink absorption characteristics, a requirement directly supported by effective particle separation upstream.
