At the end of this module, you will be able to:
- Describe the purpose and objectives of the headbox on a paper machine
- Describe the advantages of a multi-layer headbox
- Identify and locate the major components of a multi-layer headbox
- Identify stock and recirculation flows
- Describe the available adjustments to the headbox
- Identify protection and care guidelines for the headbox and forming fabrics
The following key questions are answered in this module:
Why are multi-layer headboxes increasingly popular?
Because they allow for efficient fiber usage and optimization of desired sheet properties.
Are the stock systems for multi-layer hydraulic headboxes and non-layered headboxes the same?
No. Because the different layers can have different furnish compositions, each layer has its own stock preparation and delivery system.
What are the advantages of dilution profiling systems over traditional slice lip adjusters?
Dilution profiling systems eliminate the cross-flows in the stock jet and fiber orientation variability that were caused by slice lip adjustments.
What is the purpose of the tubes, chambers, drilled plates, and flat sheets or vanes in hydraulic headboxes?
These items induce turbulence in the stock flows to keep the fibers separate and help break up flocs before the stock reaches the forming fabrics.
What happens when the slice opening is widened slightly?
The pressure inside the headbox initially drops, so the fan pump speeds up to increase the headbox pressure, which increases the total flow through the headbox. The end effect is a drop in the headbox consistency.
Below is a transcript of the video sample provided for this module:
The purpose of the headbox is to deliver low consistency stock to the forming section of a paper machine. On a modern tissue machine or twine wire paper machine, the headbox delivers the stock to a nip created by two rolls, the breast roll and forming roll, between two forming fabrics. These machines are equipped with hydraulic headboxes. Which means that they are fluid fill and fully pressurized. Note that stock is sometimes called furnish, and the forming section of a paper machine is sometimes called the former.
Use the additional resources and links below to learn more about this topic: