At the end of this module, you will be able to:
- Describe how high density cleaners differ from other centrifugal cleaners
- Identify safety hazards associated with high density cleaners
- Identify the purpose of high density cleaners
- Describe the operation of a "junk trap" during a dump cycle
- Describe the purpose of the main components of a junk trap
- Identify typical applications of high density cleaners in secondary fiber, pulp mill, stock preparation, and broke systems
The following key questions are answered in this module:
What is the purpose of high density cleaners?
Their main purpose is to separate heavy contaminants from fibers in fiber-water suspensions in order to protect downstream equipment from wear and damage.
Where are high density cleaners typically used?
They are often used in secondary fiber systems, pulp mills, paper and board machine thick stock systems, and broke systems.
How are high density cleaners different from other forward cleaners used in the production of paper and board?
High density cleaners are larger in size physically, discharge their rejects intermittently rather than continuously, and operate with higher feed stock consistencies than other forward cleaners.
What is the purpose of the elutriation water in a high density cleaner?
A continuous stream of elutriation water is used to flush fibers out of the rejects chamber, at the bottom of the cleaner, during cleaner operation.
How often are the junk traps on high density cleaners emptied?
The frequency of the junk trap dump cycle and the length of the purge depends on the level of contaminants in the stock suspension.
Below is a transcript of the video sample provided for this module:
High-density cleaners are specifically designed to remove high and medium-density contaminants or contaminants with high and medium specific gravities from stock. Contaminants such as rocks, nuts, bolts, nails, paperclips, staples, glass, and other heavy debris are removed by the cleaner. High-density cleaners are not designed to remove wax or other low-density or low specific gravity materials. The stock suspension is pumped tangentially into the top of the cylindrical cleaner body at relatively high velocity. As the stock flows inward, centrifugal force and fluid sheer create a vortex near the center of the cleaner. Dense materials move to the outside wall and drop down into a bottom rejects collection chamber. The fibers migrate to the center vortex and travel upwards to the accepted stock outlet.
Use the additional resources and links below to learn more about this topic: