It is known to use twin screw extruder for processing plastics materials where the internal processing chambers are formed by wear resistant liners. The liners have internal layers which are wear resistant to lengthen the life of the extrudingcylinder. To enable the liners to be replaced and to absorb the forces occuring in operation, the liners are surrounded by a supporting member.
When tempering casings of twin screw extruder of this type, that is to say controlling the temperature thereof, difficulty is experienced in obtaining a good even tempering action over the periphery of the spectacle shaped combined bore. Thegreatest quantity of heat per unit appears in wedge shaped projections between the two longitudinal bores of the liner, while lateral portions of the spectacle bore show less localisational heat.plastic recycling system