Package Yarn Dyeing Machine

Overview

A package yarn dyeing machine colours yarn while it is still wound on tubes, before it is ever knitted or woven. The yarn is wound onto open perforated tubes called dye packages, the packages are stacked on spindles in a carrier, the carrier is lowered into a sealed pressure vessel, and dye liquor is pumped through the packages until the colour is fully exhausted onto the fibre. Because the bath is sealed it can be run well above the boiling point of water, which is what lets polyester and polyester blends dye at all, since their disperse dyes only diffuse into the fibre near 130 C.

The defining feature of package dyeing is that the dye liquor is forced through the body of each package rather than just washed over the surface. The yarn itself is the filter bed. Getting an even shade from the inside of a package to the outside, and from the top of a tall vessel to the bottom, is the whole engineering problem the machine is built to solve.

How it works

Wound packages are loaded onto the Package Carrier, where each spindle feeds liquor up through the cores of a stack of perforated tubes and spring spacers keep the column tight as the yarn shrinks and wets out. The loaded carrier drops into the Pressure Vessel, a stainless kier whose lid is clamped down and sealed so the bath can hold several bar of pressure.

The Circulation Pump then drives the liquor through the packages at high flow. A flow reverser swaps the direction on a timer so liquor runs inside-to-out and then outside-to-in, which is the key trick for levelling the shade across the package wall. The Heating & Cooling section heats the bath with steam through an indirect exchanger on a slow controlled gradient, typically a degree or two per minute, then cools it back the same way at the end so the fibre is not shocked.

Dye and chemicals are not dumped in. The Dosing System system meters them from the Addition & Mixing Tanks into the running bath on a programmed profile so the dye strikes the yarn slowly and evenly. The Process Controller runs the whole recipe and logs the temperature curve and every addition against the batch number.

Carrier and packages

The yarn is wound soft onto a Perforated Dye Tube, an open lattice tube that lets liquor pass straight through the package wall. Winding density matters: too tight and liquor channels around dense spots, too loose and the package collapses. Stacks of tubes sit on a Carrier Spindle in the carrier, separated by a Spring Spacer that absorbs the shrink of the wet yarn so the stack stays compressed and liquor cannot bypass the package ends. A base seal on each spindle and a top compression plate force essentially all the pump flow through the yarn rather than past it.

Flow, heat and dosing

High, reversing flow is what makes the dye even. The Pump Impeller is sized for volume rather than head, since the resistance of the packages is modest but the flow needed is large. The Flow Reverser alternates direction so neither the inside nor the outside of a package sees fresh liquor first for the whole cycle.

Heat comes through the Heat Exchanger rather than direct steam injection, so steam never dilutes the bath and the gradient stays under control. Disperse and reactive dyes are sensitive to how fast they strike, so the Dosing Pump adds them gradually and the Dosing Flow Meter confirms the amount that actually reached the bath. Salt or alkali for reactive dyes is dissolved separately in the Salt Tank and dosed on its own profile.

Materials and construction

Everything wetted is austenitic stainless, usually 316L, because dye baths run hot and carry salt, acid and alkali in turn. The Vessel Shell is a welded pressure shell with relief valves and a quick-open clamped lid. The pump uses a Mechanical Seal rated for hot liquor, and the Pipework Set and tanks are all stainless. The vessel is jacketed in mineral wool to cut heat loss and protect the operator.

Variants and use

Machines range from small sample kiers holding a few kilograms to production vessels taking a tonne of yarn at a 1:6 to 1:10 liquor ratio. Low liquor ratio designs save water, energy and chemicals by holding less bath per kilogram of yarn, which has become the main selling point as effluent and energy costs rose. Package dyeing is the standard route for sewing thread, knitting and weaving yarns, and any yarn that must be coloured before fabric forming, and it competes with hank dyeing where bulk and handle matter and with fabric dyeing where colour can wait until after the cloth is made.