Real-time monitoring of barrel thickness and barrel/screw separation using ultrasound

Abstract

Ultrasonic sensors together with a fast data acquisition system have been used to monitor the barrel thickness and barrel/screw separation during low-density polyethylene as well as high-density polyethylene extrusion in 30 mm and 50 mm twin-screw extruders. The sensors include sol–gel sprayed high temperature (HT) piezoelectric thick ceramic film ultrasonic transducers (UTs), stand-alone HTUTs and air-cooled buffer rod type sensors consisting of a room temperature UT and a non-clad or clad buffer rod to which the room temperature UT is attached. The installation and use of these sensors are non-intrusive to the extruder and non-destructive to the polymers being processed. This study has demonstrated the capability of appropriately designed ultrasonic sensors in monitoring the barrel and screw integrity at the melting, mixing and pumping zones of the extruder via barrel or flange. The merits and limitations of these sensors are discussed. The measurement speed and analysis of the sensitivity for quantitative wear measurements are also presented.

Process monitoring and visualization solutions for hot-melt extrusion: a review

“…[83] Ultrasonic techniques: longitudinal waves Melting, mixing, pumping zones -Barrel integrity at melting, mixing and pumping zones, screw and barrel wear - [89] Melting, mixing, pumping zones…”

“…[88] Besides qualitative and quantitative monitoring of the polymer melt, ultrasonic sensors can be used to monitor the barrel and screw integrity at the melting, mixing and pumping zones of the extruder via barrel or flange. This application was discussed by Jen et al [89] Extrusion of lowdensity PE (LDPE) was performed on a 30-mm corotating twin-screw extruder and on a 50-mm counterrotating twinscrew extruder. Four types of high-pressure ultrasound transducers were developed and used at the melting, mixing and pumping zones of the extruder to monitor the screw and barrel wear.…”