Cotton Yarns in Continuous Wet Processing Engineering
Continuous wet processing of cotton yarns demands precise control of yarn structure, swelling draft, liquor application, and transport tension to assure performance.
Vacuum Dewatering
Fluid Extraction
Mechanical moisture extraction employs a pressure differential to pull water from a moving fabric web. Rather than relying solely on nip rollers, vacuum dewatering uses a suction slot to remove liquid from the interstices of the yarns. This method is effective for delicate fabrics that might be damaged or crushed by high pressure squeezing.
Pressure Differential
Suction pumps create a low pressure zone on one side of the fabric which forces air through the material. As the air passes through, it carries away the water droplets that are trapped between the fibres. The efficiency of vacuum dewatering depends on the air permeability of the fabric and the speed of the production line, with heavier fabrics requiring a higher vacuum setting to achieve the same result, often necessitating the use of multiple suction slots in sequence.
Reducing Consumption
Decreasing the initial moisture content before the fabric enters a drying oven significantly lowers the total energy required for evaporation. Because vacuum dewatering is a mechanical process, it is more cost effective than using heat to remove the same amount of water. Mills often install these systems before stenters or tensionless dryers.
Residual Moisture
Fabrics processed this way often reach a more uniform level of dampness than those that are only squeezed. This consistency helps in preventing drying defects like migration or uneven finish application. The final moisture pick up can be adjusted by changing the vacuum level or the slot width.