Mixing & machine chests
The mixing chest is a large, agitated tank used for mixing various types of pulp, fillers, and additives together in a specified formula for the paper machine. The mixed stock is fed to the machine chest where it is pumped to the headbox and dispensed evenly onto the moving wire of the papermaking machine. When the stock is de-watered and dried, the result is finished paper.
Level controls ensure that the chests never overflow and that the level never sinks below a safe level with respect to the agitation zone. Level monitoring must contend with pulp thickness, high humidity, and specific gravity changes. As the chest discharge operation is on level control, consistent flow must be maintained to ensure continuous papermaking.