Pulp and Paper Baskets Brochure.pdf - Johnson Screens

PULP AND PAPERSCREENSScreen rooms in many mechanical pulpand paper mills are being rejuvenatedtoday as a result of Johnson Screenssignificant breakthrough in screeningtechnology with the fine-slottedVee-Wire ® (wedge-wire) basket.This technology can yield significantlyimproved shive removal, enhancephysical pulp properties, and, in somecases, reduce electrical power.The design of the Vee-Wire basketproduces a continuous slot over thelength of the basket. Vertical, parallelrods or “wires” are arranged in a circleto form a cylindrical shape. The wiresare held mechanically in place withmetal bands or rings. The size ofthe gap or slot between the wires isprecisely set. Typical values are0.004 in., 0.006 in. and 0.008 in.(0.10 mm, 0.15 mm, and 0.20 mm).The angle of the wedge and theamount that the wedge protrudesinto the stock (i.e., the profile) effectsscreen performance.By comparison, conventional slottedbaskets are built from rolled sheet metal.Parallel slots, each several inches long,are cut into the sheet metal, leavingland areas between each slot to providemechanical strength to the basket.The Vee-Wire basket, by virtue of thecontinuous slot and slender wires, hassignificantly less land area. This resultsin approximately twice the open area asthe conventional basket for the sameslot width.For any given screen, this advantageyields the following benefits:• Lower passing velocity for a givenproduction rate and slot width.• Higher production rate for a given slotwidth and passing velocity.• Finer slots for a given production rateand passing velocity.02