Process for steam-conditioning spin-oriented polyamide filaments

An improved high speed spinning process for making partially-oriented polyamide draw texturing feed yarns with predetermined standards including the steps of extruding molten filaments of a synthetic fiber-forming polyamide from a spinneret assembly, cooling the molten filaments to a non-tacky state in a quench chimney, conditioning the cooled filaments with steam by passage through a substantially vertical conditioning tube having heated upper and lower portions, introducing steam into the tube within its heated upper wall portion, and winding up the conditioned filaments under tension into a yarn package at a speed of from 3000 to 4000 ypm and wherein the improvement comprises regulating the temperature of the lower heated wall portion independently of the upper portion as required to maintain a yarn property that varies with changes in the lower heated wall portion, within predetermined limits while maintaining steam flow in the tube substantially constant whereby the acid dyeability of the yarn remains substantially unchanged.