Pressure Screens
Pressure screens are used primarily to separate unwanted debris or contaminants from the desirable fibers in papermaking pulp. This is accomplished by flowing a pulp slurry over a surface that has many small holes or slots in it. Most of the small flexible fibers pass through the openings, and are accepted, and the larger particles which cannot pass through the openings are held back, or rejected. A typical pressure screen consists of a vertical cylindrical housing that contains a perforated cylindrical screen basket. Within the basket is a spinning rotor which supports foils or protrusions that run close to the surface of screen. Screen performance is quantified by looking at such factors as the reject rate, debris removal efficiency, and long fiber reject rate. [course outline] Pressure Screen Internal Construction Pressure Screen Baskets Pressure Screen Rotors Screening Theory 1 of 2 Screening Theory 2 of 2 Screen Performance 1 of 2 Screen Performance 2 of 2 Multiple Stage Screening Systems Pressure Screen Control Pressure Scre
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Course Details
Learning Objectives
Explain the purpose of pressure screening Identify the major components of a cylindrical pressure screen Describe how screens are kept from plugging Describe why screening systems use multiple stages List three measures of screening performance Identify controls which affect screening performance List possible causes for pressure screen process and mechanical malfunctions
Specs
Frequently Asked Questions
What is the primary purpose of a pressure screen?
What is the purpose of the spinning rotor in a pressure screen?
What advantage is gained by using cascaded screens?
What is a good strategy for unplugging a pressure screen?
What could be some causes of poor accepts quality?
Sample Video Transcript
A typical pressure screen consists of a vertical cylindrical housing which contains a perforated cylindrical screen basket. Within the basket is a spinning rotor which supports foils or shaped bumps that run close to the surface of screen. There are several variations on this design. Some screens are horizontal. Some designs have the inlet flow going to the inside of the basket, some have it going to the outside. One design employs two baskets with the flow being introduced between them. For simplicity, the rest of this module and the illustrations shown will refer to the “typical” screen described above with the feed flow going to the inside of a single basket.
