Paper Machine Twin-Wire Formers

SKU: C-640Duration: 13 Minutes

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Course Details


Training Time: 13 minutes

Compatibility: Desktop, Tablet, Phone

Based on: Industry Standards and Best Practices

Languages: English, Portuguese, French

A twin-wire former captures the stock jet in the converging nip formed between two fabric-covered rolls. These are also sometimes referred to as "gap" formers. There are four types of twin-wire formers - blade, roll, hybrid and roll/blade. Each has its own challenges and strengths. With twin-wire formers, it is especially important to define the desired sheet properties, and then work with equipment and fabric suppliers to configure, control and operate the design that is selected.

Learning Objectives

  • Identify the issues which led to the development of twin-wire formers
  • Identify and describe the four basic types of twin-wire formers, including blade formers, roll formers, hybrid formers and roll/blade formers
  • List advantages and disadvantages for each type of twin-wire former
  • Describe the challenges presented by twin-wire formers
  • Describe the advantages of twin-wire formers

Key Questions

The following key questions are answered in this module:

What are some benefits of twin-wire formers over Fourdrinier formers?
Twin-wire formers reduce sheet two-sidedness, wire instability, and the length of the forming section. Also, twin-wire formers double the drainage area and can run at higher speeds.

What are some potential problems presented by twin-wire formers?
Space limitations restrict the addition of more water-removal devices. Fibers can build up preferentially on the two fabric surfaces, which increases the likelihood of sheet delamination. Fabric selection is critical and there is a high potential for fabric and equipment damage because the fabrics operate in close proximity.

What is a roll former?
Roll formers are characterized by the stock jet being captured in a long nip created between two fabrics traveling together around a perforated suction forming roll.

What is a blade former?
Blade formers are characterized by a stock jet impinging into a gap between two forming fabrics which are fored together by a number of fixed blades in a vertical forming section.

What is a roll/blade former?
Roll/blade formers try to combine the advantages of roll and blade formers and avoid their problems. Two forming fabrics wrap around a perforated suction roll then there is a blade section to provide additional pulsed drainage.

Sample Video Transcript

Below is a transcript of the video sample provided for this module:

A twin-wire former captures the stock jet from the head box in a converging nip formed between two rolls, which are covered by two moving fabrics or wires. They are also sometimes referred to as gap formers. Twin-wire former designs have changed and evolved over the years and have developed somewhat differently for different paper and board grades. It is worth noting that the forming section of a paper or board machine, whether fourdrinier, twin-wire, or some other design has a major impact on the fundamental properties of the sheet and the runnability of the machine.
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