Boundaries to Normal Operation (cont’d)
Flow to the press is controlled by either a tank level controller or some type of
production rate control. The consistency is typically controlled by the operator, who
chooses a desired consistency setpoint for the controller. This might be a single point
for all operating rates, or it might be similar to what is shown here, with two
consistency setpoints with some overlap of flow rates.
The recommended operating strategy is to start up with at least the minimum flow as
quickly as possible. This is shown as step No.1 above. This might take 10-30 seconds,
depending on how the flow controller and valve respond. The flow should now stay
above this minimum flow.
Once started, the remaining feed system can be started to increase the consistency to at
least the minimum boundary. The consistency controller can be set in automatic at the
lower setpoint as shown by the dark area to the left inside the acceptable operating
range. As the consistency comes up to this setpoint, the production rate increases
following line No.2 above.