Double Posi-Pulse Blade
Provides controlled activity and drainage when it is difficult to generate sufficient activity with a conventional foil.
How it works
Activity Generation - as water drains through the fabric, a converging nip produced by the lead angle of the blade and the fabric forces the water back into the sheet. This produces a shear force capable of breaking the fiber mat and penetrating through the stock slurry, refluidising the slurry and breaking the fiber flocs.
Controlled Drainage - because the blade reintroduces water into the stock, the drainage rate can be controlled. This maintains fiber mobility further down the table, providing the opportunity for formation improvements.
Application Guidelines
Paper Grades
The recommended grade structures conducive to this blade are heavier-weight grades; pulp, bleach board, heavy-weight liner and heavy fine grades.
Machine Speeds
The most potential exists on the slow speed grades, less than 1200 fpm. However, Posi-Pulse blades have run from medium speeds up to 2000 fpm with good results.
Position
The blade should be used early in the table where more water is present. These blades are typically positioned on the first gravity foil position structure following the forming board but can also be used in the trailing blade position of the forming board.
Material
Posi-Pulse blades are currently available in Duwear Polyethylene & Ultrasert F.
Blade Spacing
Uniform spacing is recommended to create a frequency above 60Hz.
Ingoing Angle
It is recommended that the ingoing angle be 3° to 21°, typically in 3° increments. The angle is dependent on grade and basis weight.
Top Flat
The objective of the top flat is to seal the fabric to the blade to create a positive pressure pulse. A length of ½ inch is most common.
Exiting Angle
The exiting angle pulls water through the fabric so water can be reintroduced by the following Posi-Pulse blade. Angles from 0-3° have been used, dependent on grade and position.
Negative and Positive Angles
The quick negative and positive angles are used to create additional activity. These angles are typically equal and range from 5° to 15° increments.