Dust collectors are needed in plastics processing facilities because conventional high-speed vacuum-conveying systems move plastic pellets and flakes so quickly that some are damaged, causing dust and other problems. Pellets of relatively hard materials can chip or shatter when they hit tube walls or corners, creating “fines” such as small pieces, particles or dust.
Fines and dust should be removed before plastic resin is processed into parts. Otherwise, they will melt much more quickly than undamaged pellets and could begin to burn, leaving blackened or discolored specks or streaks in finished parts. Removing dust from undamaged pellets typically requires a two or three step approach, explained and detailed in the picture below:
- Dust removal begins with material receivers. By equipping receivers with 20 mesh stainless-steel screen on the vacuum air, fines that are suspended in the conveyor airstream separate from the pellets (which fall into the receiver). Then, the fines pass through the screen and are carried in the central vacuum line back toward the vacuum source.
- Typical vacuum conveying systems provide a central Dust Collector, usually consisting of a fixed cartridge-style filter, to protect the vacuum pump by removing fines from the vacuum airstream. The central Dust Collector does the bulk of the dust collection—and requires regular cleaning/maintenance—unless a “cyclone” dust collector is added.
When processors add a “cyclone” dust collector, they do it to improve dust collection efficiency and reduce the load on the central dust collector. As shown below, Cyclone dust collectors are always placed just ahead of the central dust collector.
How cyclone dust collectors work.
The vacuum airstream, containing the fines and dust, enters the cyclone dust collector tangentially. The air spins in a circular/cyclonic motion as it is pulled through the chamber of the Cyclone collector toward the vacuum pump. This high-speed rotation creates centrifugal force that drives the heavier plastic particles, fines, and dust outward toward the wall of the Cyclone chamber. They hit the wall, lose velocity, and fall down into a dust collection canister, hopper or bin located underneath the cyclone collector.
Adding a cyclone dust collector ahead of the central dust collector and vacuum pump offers major benefits for plastics processors:
- Dust, and fines are easily removed to ensure maximum part quality.
- It dramatically reduces the amount of dust that must be captured in the pleated filter cartridge of the central Dust Collector. Service for this filter is needed much more frequently and is much more difficult unless a cyclone dust collector is in place.
- Because dust falls out of a cyclone dust collector into a bin, it is much easier to maintain. Normally, the only regular maintenance is to empty and replace the dust bin.
- It helps to maximize conveying system performance and reliability. The risk of degraded conveying system airflow and performance due to clogged central filters is greatly reduced.
- For added convenience, cyclone dust collectors offer an “Auto Dump” feature that automatically empties the dust-collection bins into larger Gaylord boxes located below. This enables continuous dust collection without the need to manually empty the dust collection bin.