Singeing

introduction to singeing

1. Singeing

2. Singeing is a process applied to both yarns and
fabrics to produce an even surface by burning off
projecting fibres, yarn ends, and fuzz.
Objectives
Production of smooth and clear fabric surfaces
To minimize soiling of fabric
To avoid skittery dyeing
To reduce risk of pilling specially in synthetics and
blends
To enhance the quality of fabric


Definition

4. Improved end use and wearing properties
Increased lusture (reflection of light)
Less pilling
Less soil attachment
Bright shades in dyed fabric
Fine intricate patterns in printed fabrics
Advantages of singeing

5. Burning behaviour of textile materials

6. Burning behaviour of textile materials
Pyrolysis
•Pyrolysis refers to transformation of a substance by the
action of heat. At temperature of pyrolysis (Tp), both
thermoplastic and non-thermoplastic fibres
decompose (pyrolyze) into lower molecular weight
fragments. The chemical change, which begins at
temperature of pyrolysis, continues through the
temperature of combustion(Tc).

•Exothermic pyrolysis (cellulose)
•Endothermic pyrolysis (synthetic fibres)

7. •There are three main types of singeing
machines:
•Plate singeing machine
•Rotary-cylinder singeing machine (roller
singeing machine)
•Gas singeing machine
Types of singeing machines

8. Plate Singeing Machine
•In this type of singeing machine, the cloth
passes over and in contact with one or two
heated curved copper plates. The thickness of
the plates ranges from 1 to 2 inches. The
heating of the plates is done by a suitable
burning arrangement of gas mixed with air.
The plates are heated to bright redness and
the cloth passes over and in contact with
these plates at a speed ranging from 150 to
250 yards per minute.

9. •The passage of the cloth can be arranged in such a manner
that one or both sides of the fabric may pass over and in
contact with the heated plate(s), in order to accomplish
singeing of one or both sides of the fabric in a single
passage.

Disadvantages
•Uneven singeing due to local cooling of hot metal surface
•Groove formation on the plate surface

Remedies
•In order to avoid local cooling of a certain part of the
plate(s) by constant passage of cloth over it, an automatic
traversing mechanism is fitted to the machine. This
mechanism brings the cloth into contact with a constantly
changing part of the plate(s), not only to avoid local cooling
but also local wearing of the plate(s).

10. Rotary-Cylinder Singeing Machine
•In this type of singeing machine, the cloth passes
over and in contact with a heated rotary cylinder
made of copper or cast iron. The rotary cylinder
has internal firing and revolves slowly so that
constantly a fresh surface of the roller comes in
contact with the cloth. The direction of rotation
of the cylinder is opposite to the direction of the
fabric so that the protruding fibres or nap of the
fabric is raised.
•This type of machine is particularly suitable for
the singeing of velvets and other pile fabrics

11. •If the singeing of both sides of the fabric is required, then two
cylinder are employed, one for each side of the fabric.






Line diagram of rotary-cylinder singeing machine

12. Gas Singeing Machine
In this type of singeing machine, the fabric passes over
a burning gas flame at such a speed that only the
protruding fibres burn and the main body of the
fabric is not damaged by the flame. This is the most
common type of machine used for singeing fabrics as
well yarns

13. Gas Singeing Machine
Main parts
•Tension unit with guide rollers and bars
•Pre-brushing with suction
•Singeing chamber with exhaust
Water cooled roller
Ignition system
Carburetor with blower
Burners
•Post brushing with suction
•Quenching box (desizing unit)
•Desizing mangle

14. Gas Singeing Machine
Main parts
•Tension unit with guide rollers and bars
•Pre-brushing with suction
•Singeing chamber with exhaust
Water cooled roller
Ignition system
Carburetor with blower
Burners
•Post brushing with suction
•Quenching box (desizing unit)
•Desizing mangle

15. Gas Singeing Machine

16. Gas Singeing Machine
Tension unit with guide rollers and bars
•Ensures the crease free entry of fabric
Pre-brushing with suction
•Removes the dust, dirt, lint and loose fibres adhered to
fabric
•Causes the fibres sticking to fabric surface to stand out
for easy burning
Brushing roller
Brushing and
beating roller
Beating roller

17. Singeing chamber
•Two burners for both side singeing of fabric
•Cooling system for burners
•Water cooled rollers
•Ignition of gas
•Gas and air mixture

Post brushing with suction
•To remove the ash on fabric surface

Quenching box
To distinguish residual flame
To apply desize solution
Padding mangles
To transport the chemical from surface to core of fibre
To remove the surplus chemical
Gas Singeing Machine

18. 1.Flame intensity
2.Fabric speed
3.Singeing position
4.Distance between flame burner and fabric
5.Flame width
Singeing parameters

19. Flame intensity
•Amount and speed of air-gas mixture
•Flame temperature at mouth of burner
1250-1300 C
•Speed of flame 15-35 m/sec
•Flame intensity 5-20 mbars

Fabric speed
•Depends upon fabric ariel density

20. Singeing position
•Singeing onto free guided roller
•Singeing onto water cooled roller
•Tangential singeing
Singeing onto free guided roller
Singeing onto water cooled roller
Tangential singeing

21. Distance between flame and burner
•Singeing efficiency decrease on increasing
distance
•Distance is usually 6~8 mm, can be adjusted
to 6~20 mm.
Essential conditions for good singeing
•Flame with high mechanical and thermal
energy
•Uniform flame
•Optimum flame fabric contact time

22. Pre-requisite for singeing
•Full dry fabric
Fabric parameters to be considered for
optimum singeing
•Fabric construction
•Fabric thickness
•Heat sensitivity

23. Important consideration
•Flame should be bluish
•Proper threading of machine
•Regulate fabric speed
•Checking of burner nozzles
•Check the exhaust blowers

Evaluation of singeing fabric
•Magnifying glass
•Scotch tape
•Pilling test

24. Incomplete singeing
Too low flame intensity
Too fast fabric speed
Too far distance between the fabric and the burner
Inappropriate (i.e. less severe) singeing position
Too much moisture in the fabric incoming for
singeing.


Problems in gas singeing

25. Uneven Singeing Across the Fabric Width

Non-uniform moisture content across the fabric
width
Non-uniform flame intensity (uneven flame height)
across the fabric width
Uneven distance between the burner and the fabric
This may be due to misalignment or improper
setting of the guide rollers
Uneven smoke evacuation over the burners


Problems in gas singeing

26. Uneven Singeing Along the Fabric Length

Non-uniform moisture content along the fabric
length
Non-uniform flame intensity along the fabric
length
Variation in gas-air mixture supply
Increasing or decreasing thermal energy of the
flames during production
Change in fabric speed during singeing
Change in the distance between the fabric and
the burner along the length


Problems in gas singeing

27. Over-singing or Thermal Damage of the
Fabric

Too high flame intensity
Too slow fabric speed or too long contact time
between fabric and flame
Too close distance between the fabric and the
burner or too deep penetration of the singeing
flame into the fabric
Inappropriate (i.e. too severe) singeing position


Problems in gas singeing

28. Formation of Small Beads of Molten Material

Insufficient energy supply, when the thermal
energy is not supplied quickly enough to be able to
ignite the thermoplastic fibre rather than melting it.


Problems in gas singeing