2006-03-04 · rpm=screw rotations/min. For example: A 40-mm twin-screw extruder is processing a mineral-filled PP at 160 kg/hr, running at 400 rpm with a %torque of 68%. The machine has a 56 kW (approx. 75 hp) motor and a maximum possible screw rpm of 600. kW (applied)=56 kW x .68 x 400/600 x .97=.154 kW per kg/hr.