Abstract: The production capacity of a conventional high pressure feeder having a pocketed rotor with a slotted screen at the low pressure outlet port is significantly increased by constructing the screen so that its arcuate bars have a width much less than normal, and thus a much greater open area of the screen is provided. Structural integrity is maintained by providing a reinforcing bar extending transverse to the arcuate screen bars, typically attached at the convex mid-point area. The screen is formed from a cast metal body, and the width of the arcuate screen bars is typically between about 0.14-0.20 inches.

Abstract: The efficiency of a diffuser, for washing or bleaching paper pulp, is enhanced by taking steps to ensure that the approximate upstroke speed is only slightly faster than the pulp upflow velocity, to provide an early warning indication of the tendency of the diffuser screens to plug, and to prevent upward movement of the screen, after completion of a downstroke, uncontrolled by the hydraulic system designed to effect movement. The pressure under the annular screen is sensed and compared to normal static pressure at the elevation of the screen by a D/P cell in a leg, and a computer controls the hydraulic system so that the screen upstroke speed is only slightly faster than the pulp upward speed. Early detection of a tendency to plug is provided by a pressure sensor within the hollow interior of the screen spaced from the screen orifices.