March 2012

Engineering Case Histories

Case 67: Extruder blowback

Understanding what is happening can lead to a solution

Sofronas, T., Consulting Engineer

An extruder is a unit that compresses a product and then pushes it through a die. Extruders are used in the hydrocarbon processing industry, especially in polymer production. One operational problem that can occur is called “blowback.” A blowback occurs when the processing conditions are such that the machine can no longer push the material through the die. It (the product) “blows back” from the discharge point through the screw and out the feed end. This is similar to what occurs when gases in centrifugal compressors surge back to the product inlet. However, the blowback in extruders is usually from steam or other volatiles present in the material being extruded. Blowb

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