Soft Flow Dyeing Machine: Features, Types and Working Principle
M. Hossen Uzzal
B.Sc. in Textile Technology
Monno Fabrics Ltd. Manikgonj
It was found that in using Winch dyeing machines, there were some inherent problems. So the Jet dyeing machines when they came up in the 1970’s 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.
Modern Jet dyeing machine are three types:
- Overflow Dyeing Machine
- Soft-flow Dyeing Machine
- Airflow Dyeing Machine
In this article I will discuss on soft flow dyeing machine.
Soft Flow Dyeing Machine:
In the past, winch machines were used to dye knitted fabrics, with a material to liquor ratio of 1:20. A soft flow dyeing machine needs only 4 L of water for every 1 kg of fabric processed. Now, a new range of dyeing machines is available with an M:L ratio even lower than 4. In soft flow dyeing machines, the fabrics are circulated using the liquor, which needs some amount of liquor.
In the soft flow dyeing machine, water is used for keeping the fabric in circulation. The conceptional 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.
There are several versions of both jet dyeing and soft flow dyeing machines. Some designs have two or more tubes, mounted side by side, which share a common dye liquor. The speed of the rollers, the circumference of the tube and the force of the jets can be altered to accommodate different fabrics and reduce potential issues of fabric creasing and any stretching of the fabric, thereby making the machines versatile in the range of fabrics that can be processed.
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.
- Machine pressure vessel and major wet parts made of stainless steel AISI 316/ 316 L, highly corrosion resistance material.
- Heavy duty stainless steel centrifugal pump for optional dye liquor circulation. Highly efficient heat exchanger for fast heating and cooling.
- A stainless steel filtering device placed in such a way for easy cleaning.
- A unique design of jet nozzle can provide high discharge of liquor with subsequent pressure to ensure fast movement of fabric transport upto 300 meter / min., and the speed of fabric can be adjusted, required to desire quality.
- A mirror polished fabric transport perforated basket for easy trouble free movement of fabric from back to the front of machine, perforated basket fabricated in such a way that welding part does not come in contact with fabric.
- For preparing chemical, color kitchen tank is provided made out of stainless steel 316, with required valves for auto dozing.
- All valves is made of investment casting and is of stainless steel 3l6.
- Electrical control panel with microprocessor to operate the machine is provided with pneumatic control circuits.
- Magnetic level indicator duly calibrated for correct liquor measurement.
- Take off reel with direct couple geared motor and stainless steel structure
- All safety device required for a pressure vessel is incorporated with the machine.
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.
1. Multi Nozzle Soft Flow Dyeing Machine:
- Very low liquor ratio – around 1:1 (Wet Fabric).
- Can reach high temp. up to 140°C.
- Easily dye 30 to 450 g/mt.sq. of fabrics (woven and knitted fabrics).
- Work as a jet dyeing machine for polyester and blend fabrics.
- Work as a soft flow machine for cotton fabrics.
- Number of very soft-flow nozzles.
- No pilling effect.
- Wide capacity.
- Capacity 50 to 2000kgs.
2. High Temperature High Pressure Soft Flow Dyeing Machine:
- Compact body made of stainless steel.
- High efficiency heat exchanger for quick heating/cooling.
- Compact body made of stainless steel.
- Heating rate – around 4°C/Min up to 900°C – around 3°C/Min up to 135°C At steam pressure of 6 Bar.
- Cooling Rate- around 4°C/ Min At water pressure of 4 Bar and 15°C.
- Maximum working temp is 135°C.
- Maximum working pressure of 3.2 Bar.
- Control manual as well as automatic.
- Heavy duty stainless steel pump.
Working Principle of Soft Flow Dyeing Machine:
In soft flow dyeing machine, the fabric rope and the dye liquor move only slowly, giving a gentler mechanical action. The main dye vessel is tubular in shape and contains the bulk of the fabric. A circular driven reel gently lifts the rope from the dye liquor and feeds it into the vessel down, which it progresses to a narrow transportation tube that delivers the fabric back to the reel. Some machines use a jet to transport the fabric that provides greater speeds, but this does sacrifice some of the gentle action. The transportation tube can be located above or below the main vessel and is filled with dye liquor. The fabric rope experiences no tension, so the machine causes less creasing of delicate fabrics.
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:
- In which fabric is circulated
- In which dye bath is circulated
- In which both the bath and material is circulated.
Soft flow dyeing machine is the best example of a machine that circulated both the fabric and the dyebath. It is used for knitted fabrics. For Terry-towels soft flow dyeing is use.
In soft flow 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.
In soft flow dyeing machine, 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. 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. These machines use a jet having lower velocity that that used on conventional jet dyeing machines. The soft flow machines are gentler on the fabric than conventional jet machines.
- Textile Dyeing by Dr. N. N. Mahapatra
- An Introduction to Textile Coloration: Principles and Practice by Roger H. Wardman
- Water in Textiles and Fashion: Consumption, Footprint, and Life Cycle Assessment Edited by Subramanian Senthilkannan Muthu
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.