Jet Dyeing Machine

Overview

A jet dyeing machine dyes fabric in rope form inside a sealed pressure vessel. The two ends of a fabric batch are sewn together to make a continuous loop, the loop is loaded into the vessel, and the machine then circulates dye liquor and moves the rope around a closed path for the length of the dyeing cycle. Because the vessel is pressurised, the liquor can be heated above its atmospheric boiling point, up to about 140 °C, which is needed to dye polyester and many polyester blends with disperse dyes. The defining feature is the jet: a venturi nozzle that converts pump pressure into a fast stream of liquor, and that stream drags the fabric rope through a transport tube rather than relying only on a winch. Compared with older winch becks, the jet gives strong liquor-to-fabric contact, even dye uptake, and lower liquor ratios.

Jet machines are the workhorse of exhaust dyeing for knits and lightweight wovens. A single vessel handles one rope; multi-tube machines run several ropes in parallel chambers off shared utilities, so a plant can dye 1,000 kg or more in one batch. The fabric is dyed in a relaxed rope state, which suits stretch and knit goods that would crease or mark if dyed flat.

How it works

The fabric rope sits coiled in the lower Rope Storage Chamber of the Pressure Vessel. The Circulation Pump draws liquor from the vessel sump, sends it through the Liquor Filter Unit and the Heat Exchanger, and delivers it to the Jet Nozzle (Venturi). At the nozzle the liquor accelerates through a narrow venturi gap and forms a jet that grips the rope and pulls it along the Transport Tube. The rope leaves the tube, plaits back down into the storage chamber, and the loop continues so every part of the fabric passes the jet many times per cycle. A driven Winch Reel assists the jet and sets how fast the rope turns over, typically a full loop every two to four minutes.

The Heat Exchanger is an indirect shell-and-tube unit. Steam through the tubes heats the circulating liquor; cooling water through the same tubes brings it back down. Heating and cooling are ramped at a controlled 2–4 °C per minute so the dye exhausts onto the fibre evenly and the fabric is not shocked. A side Chemical Addition Tank holds the dyes, salt, alkali, and auxiliary chemicals, and the Dosing Pump meters them into the loop on the recipe's schedule rather than all at once.

Subsystems

The Jet Nozzle and Transport Tube assembly is the heart of the machine. The venturi nozzle gap is set by an adjustment ring so the same machine can run light knits or heavier wovens, and the transport tube carries a low-friction liner to protect the fabric surface. Most chambers use one or two nozzles; a multi-chamber machine repeats the whole jet-and-tube loop per chamber.

The Liquor Circulation System sizes the pump for both head and flow: enough pressure to form the jet and enough volume to keep the rope moving without dragging. The pump runs off a Variable-Frequency Drive so flow can be trimmed to fabric weight. The Liquor Filter Unit traps lint and fibre fragments shed by the rope; without it the nozzle gap and exchanger tubes would foul within a few batches.

The Fill, Drain and Valving plumbing sets the liquor level, which fixes the liquor ratio, and dumps spent baths fast between dyeing steps. A large drain valve matters because a full machine may turn over several baths in one cycle (scour, dye, rinse, soap), and drain time is dead time. The Control System and HMI ties it all together: a PLC runs the stored recipe, the touchscreen HMI shows temperature, pressure, and step progress, and a Pressure Sensor guards the vessel.

Materials

The wetted parts of the machine see hot, often alkaline or acidic, salt-laden liquor, so the vessel, pump, exchanger, and piping are 316L stainless steel. The transport tube liner is PTFE or a polished stainless surface to avoid abrading or marking the fabric. Seals at the loading door and shaft penetrations are silicone or PTFE rated for the working temperature. Insulation around the vessel is mineral wool under stainless cladding, which holds process heat and keeps outer surfaces safe to touch. Bearings and the pump mechanical seal are the main wear items and are chosen for continuous hot-wet duty.

Variants

Machines split by how the fabric is moved and how lean the bath runs. Soft-flow and airflow designs carry the rope on a cushion of liquor or a stream of air plus liquor, which lets them reach very low liquor ratios near 1:4 and cuts water, chemical, and energy use per kilogram. High-temperature machines run pressurised to 140 °C for disperse dyeing of polyester; atmospheric machines top out near 98 °C for cotton and viscose with reactive dyes. Single-tube machines dye one rope; multi-tube machines run two to eight ropes in parallel for higher batch weight off one set of utilities and one controller.

Use

Jet machines exhaust-dye knitted and woven fabric in rope form: cotton and cotton blends with reactive dyes, polyester and polyester blends with disperse dyes, and elastane-containing stretch fabrics that must stay relaxed. A run loads the sewn rope, fills to the set liquor ratio, scours, dyes through a heated profile with timed chemical additions, then rinses and soaps before draining. Routine care centres on the wear items: clean the Lint Basket every batch, inspect the nozzle gap and tube liner for wear, check the door seal, and service the pump seal and bearings on schedule. Kept clean and in adjustment, a jet machine dyes evenly batch after batch with little fabric handling between steps.