Vent Flow for Multiple-Stage Extruders

Screw and barrel wear can reduce the performance of the extruder by causing the specihc rate to decrease and the discharge temperature to increase. Screw wear is discussed in Sections 13.2 and 13.4.1. Although extremely rare, wear in the feed casing can lead to a rate reduction and process instabilities. This case study is presented in Section 12.7.7. 

Two-stage and multiple-stage vented extruders are commonly used to remove volatile components from molten resin streams prior to downstream processing. The vent ports can be open to the atmosphere, or they can be attached to elaborate vacuum systems. For very specialized systems, stripping agents such as water, nitrogen, and carbon dioxide can be added upstream of the vent, mixed into the resin stream, and then devolatilized in the vent area. This technique can be employed to remove difficult components or components at a higher rate from the resin. 

This edge is flush with the inside barrel wall 

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