Automatic headbox dilution
Automatic headbox dilution is used to obtain a very even MC profile in the pulp sheet.
Based on the reading by the scanner after the dryer, the dilution valves at the headbox are activated in order to correct the profile by adding more or less dilution water to a certain area.
Dilution MD control
- Closed control loop
- Based on dry-end scanner basis weight profiles in MD
- Basis weight controlled by stock pump
- The amount of stock is varied, while the amount of water added is constant.
- The consistency in MD of the resulting web can be controlled in this way.
Dilution CD control
- Closed control loop
- Based on dry-end scanner basis weight profiles in CD
- Dilution controlled by headbox dilution profiling valves with actuators
- Cross direction basis weight profile adjusted by varying consistency into flow tubes
- While consistency is varied in cross direction, the flow rate remains constant.
- Manual or automatic valve positioning for profile adjustment.