It was found that in using Winch machines, there were some inherent problems. So the Jet dyeing machines when they came up in the 1970s were specifically designed to overcome those shortcomings.
In the Jet dyeing machine the reel is completely eliminated. A closed tubular system exists where the fabric is placed. For transporting the fabric through the tube a jet of dye liquor is supplied through a venturi. The Jet creates turbulence. This helps in dye penetration along with preventing the fabric from touching the walls of the tube. As the fabric is often exposed to comparatively higher concentrations of liquor within the transport tube, so little dye bath is needed in the bottom of the vessel. This is just enough for the smooth movement from rear to front. Aqueous jet dyeing machines generally employs a driven winch reel along with a jet nozzle.
The following diagram explains the functioning of a Jet dyeing machine:
Types of Jet Dyeing Machine:
In deciding the type of dyeing machine the following features are generally taken into consideration for differentiating. They are the following. Shape of the area where the fabric is stored i.e. long shaped machine or J-box compact machine. Type of the nozzle along with its specific positioning i.e. above or below the bath level. Depending more or less in these criteria for differentiation following types of Jet Machines can be said to be as developments of the conventional jet dyeing machine.
1. Overflow Dyeing Machine
2. Soft-flow Dyeing Machine
3. Airflow Dyeing Machine
Advantages of Jet Dyeing Machine:
The Jet Dyeing Machine offers the following striking advantages that makes them suitable for fabrics like polyesters.
Low consumption of water
Short dyeing time
Can be easily operated at high temperatures and pressure
Comparatively low liquor ratios, typically ranges between 1:4 and 1:20
Fabrics are handled carefully and gently
Soft Flow Dyeing Machine:
In the soft flow dyeing machine water is used for keeping the fabric in circulation. The conception difference of this equipment from a conventional jets that operates with a hydraulic system is that the fabric rope is kept circulating during the whole processing cycle (right from loading to unloading). There is no stopping of liquor or fabric circulation for usual drain and fill steps. The principle working behind the technique is very unique. There is a system for fresh water to enter the vessel via a heat exchanger to a special interchange zone. At the same time the contaminated liquor is allowed channel out through a drain without any sort of contact with the fabric or for that matter the new bath in the machine.
Key Features of Soft flow Dyeing Machine:
Significant savings in processing time.
Savings in water that is around 50%.
Excellent separation of different streams results in optimum heat recovery and a distinct possibility of further use or a dedicated treatment.
Principle of Soft Flow Dyeing Machine:
Textile material can be dyed using batch, continuous or semi continuous process.
Batch processes are the most common method used to dye textile materials. There are three general types of batch dyeing machines:
1. In which fabric is circulated
2. In which dye bath is circulated
3. In which both the bath and material is circulated.
Jet dyeing machine is the best example of a machine that circulated both the fabric and the dye bath. Jet dyeing is used for knitted fabrics. For Terry-towels soft flow dyeing is use. In jet dyeing machine the fabric is transported by a high speed jet of dye liquid.
As seen in the figure, this pressure is created by venturi. A powerful pump circulates the dyed bath through a heat exchanger and the cloth chamber. Cloth guide tube helps in circulation of fabric.
Types of Soft Flow Dyeing Machine:
A few of the commercially popular brands along with their particular technical specifications are discussed here. The categories are not exhaustive as such.
Multi Nozzle Soft Flow Dyeing Machine:
1. Very low Liquor ratio - around 1:1 (Wet Fabric)
2. Can reach high temp. up to 140°C
3. Easily dye 30 to 450 g/mt.sq. of fabrics (woven & knitted fabrics)
4. Number of very soft-flow nozzles
5. No pilling effect
6. Wide capacity
High Temperature High Pressure Soft Flow Dyeing Machine:
1. Compact body made of stainless steel.
2. High efficiency heat exchanger for quick heating/cooling.
3. Compact body made of stainless steel.
4. Heating rate - around 4°C/Min up to 900°C - around 3°C/Min up to 135°C At steam pressure of 6 Bar.
5. Cooling Rate- around 4°C/ Min At water pressure of 4 Bar and 15°C.
6. Maximum working temp is 135°C.
7. Maximum working pressure of 3.2 Bar.
8. Control manual as well as automatic.
9. Heavy duty stainless steel pump.
Soft Flow Dyeing Machine
1. The vigorous agitation of fabric and dye formulation in the cloth increases the dyeing rate and uniformity. It minimizes creasing as the fabric is not held in any one configuration for very long. The lower liquor ration allows shorter dye cycles and saves chemicals and energy.
2. In soft flow dyeing machines the fabric is transported by a stream of dye liquor. However, the transport is assisted by a driven lifter reel.
3. These machines use a jet having lower velocity that that used on conventional jet dyeing machines.
4. The soft flow machines are gentler on the fabric than conventional jet machines.
This article was originally published in Textile learner blog run by Mazharul Islam Kiron.