Pulp stock is stored in varying densities in horizontal or vertical "chests" that are quipped with an agitator that keeps the stock in suspension. A tower is a larger vessel that provides retention time and a down/upward flow out of pulp. Because pulp can carry residual oxidants that cause corrosion of storage vessels, vessel interiors are lined with resistant materials.
Level measurement of storage vessels is necessary to maintain a consistent supply of pulp stock to the paper machine. Pulp vessels represent a level measurement challenge due to thick and sticky media, high temperatures, steam in the vapor space, agitation, and the slightly corrosive and abrasive effects of the slurry.