Method for paper machine stock pond consistency control

Abstract

Papermachine stock consistency is regulated while carried along a forming wire table. A variable draft vacuum box disposed beneath the forming wire to draw water from the wire carried stock is automatically adjusted in response to the summation of signals from several sources. A radioactive mass measuring gauge having a sensor head positioned beneath the forming wire downstream of the vacuum box provides a signal value indicative of the total mass carried above the sensor head. From this mass measuring gauge signal is deducted a value representative of the wire mass; the remainder representing the stock mass comprising a mixture of fiber and water. The quantity of fiber in the stock mixture, independent of the water, is determined by a dry basis weight measure of paper made from the stock. A signal value representative of the fiber basis weight is divided by the stock mass signal value to yield a consistency signal value. The consistency signal value is compared to a set-point signal value for determination of a vacuum box control signal.