duster
A revolving wire-cloth cylinder which removes the dust from rags, etc.
duster: the first filter in rag pulping
A duster is a rotating cylinder lined with wire cloth that sits at the head of a rag engine or beater. Its job is to knock dust, soil, and foreign matter out of sorted rags before they enter the main pulping process. The cylinder rotates at moderate speed, typically 40 to 60 rpm, and the centrifugal action flings loosely adhered particles outward against the wire screen; these particles fall or are blown away while the rags themselves continue into the next stage.
The wire cloth covering the cylinder is typically 16 to 30 mesh, coarse enough to pass fibres but fine enough to catch lint, talc, and ground pigment that would otherwise foul the beater or contaminate the finished pulp. The cloth must be taut and evenly mounted, as sagging causes uneven drying and allows heavy debris to lodge inside the drum. Wear is steady, and the wire must be checked regularly for holes or loose areas.
Operation and placement
A duster always sits upstream of the main beating process. Rags enter at one end (usually the top centre) and the drum's rotation creates a lifting and cascading action. Dust and small particles exit through a chute at the base or through a suction hood, while the cleaned rags drop through or are carried forward to the beater inlet. Some dusters employ a light fan or air current to help carry away the finest dust, improving separation.
The term 'duster' is straightforward: it dusts. It reflects the 19th-century origin of rag pulping, when rags were hand-collected from textile mills and rags bins, carrying heavy loads of lint, dye dust, and factory debris. The duster remains essential in mills that still use rags, though synthetic fibres and virgin wood pulp have reduced rag pulping to a small sector supplying specialty papers such as currency stock, archival grade, and high-quality writing papers.
Poor dusting leads to clogged beaters, streaking in the finished sheet, and increased wear on downstream equipment. A clogged or worn duster must be stopped and the wire cloth cleaned or replaced; this maintenance is routine but necessary to maintain throughput and pulp quality.