operation of the surge pump extruder

Steady-state operation of the surge pump extruder is shown by the first 400 minutes in Figures 5 and 6. The data for these figures were from the same production run. The extruder was running a high-impact polystyrene (HIPS) resin at 2250 kg/h and a screw speed of 99 rpm for a specific rate of 22.7 kg/(h rpm). This specific rate was about 14% higher than the specific rotational flow rate calculated for the first-stage metering section, indicating that a negative pressure profile exists in the section. The negative pressure gradient is expected for a first-stage metering section of a vented screw that is operating properly; the first-stage metering section was full of resin.

To maintain the stability, the surge pump extruder screw speed was reduced such that extruder was operating at about 70% of its potential maximum rate. That is, at screw speeds higher than 99 rpm the extruder was more likely to transition from a stable to an unstable operation.

Pump inlet (extruder discharge) and outlet pressures and motor current for stable and unstable extrusion for a large-diameter extruder running HIPS resin.