In this study, we report the design and results of the operation of a modified extrusion equipment with spinning fiber devices. The performance of the equipment has been evaluated by producing polyester fibers from different recycled poly(ethylene terephthalate) (PET) of pharma- and bottle-grade. Flow performance along the extruder length was modeled and the pressure was calculated at standard conditions and considering a flow change of +10% in these standard conditions. The variation of drop pressure inside the extruder was modeled as a function of the Inherent Viscosity (IV) and humidity content (X). In addition, losses of IV were calculated in the temperature range from 290 to 300 ºC for different initial PET Viscosity index (IV₀). We report the variation of mass flow as a function of pressure applied to the extruder at different temperature for PET recycled of pharma- and bottle-grade. The proposed model for analyzing the mass flow showed a good agreement with the experimental data showing a mean error < 3 %.