The table describes the interaction of many variables on the operation of the DPA
press. The arrows indicate the direction dependent variables move following the
change of one independent variable (shown as arrows inside a circle). This table is
meant to be a general guide to explain the theory of these variables.
Consider, for example, an increase in the torque set point. This is shown at the top line
of the table. From this line, the arrows indicate that the roll speed is reduced, and the
discharge consistency (dryness out) increases. This assumes that there is no change in
the A-nip (roll distance) or pulp feed flow, consistency and temperature as all of these
are shown with an X.
The table is not a precise guide to operating the press, as there are no large and small
arrows to give some order of magnitude for changes. For example, the vat pressure is
theoretically affected by a change in roll speed. However, there is practically no
change over a wide range of operation. However, when the change begins, it can be
quick and large. It then follows the direction shown in this table.
The primary factors affecting the operation of the press are amount of pulp fed to the
press, its temperature and drainage characteristics (fiber length and pH). If these three
parameters are relatively stable, then an operator can estimate discharge consistency
from the relationship of roll speed and torque. The motor load on the shredder
conveyor will also indicate discharge consistency more than it does
production rate.