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Singeing

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introduction to singeing

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Singeing

  1. 1. Singeing
  2. 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
  3. 3. 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
  4. 4. Burning behaviour of textile materials
  5. 5. 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)
  6. 6. • 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
  7. 7. 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.
  8. 8. • 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).
  9. 9. 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
  10. 10. • 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
  11. 11. 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
  12. 12. 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
  13. 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. 14. Gas Singeing Machine
  15. 15. 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
  16. 16. 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
  17. 17. 1. Flame intensity 2. Fabric speed 3. Singeing position 4. Distance between flame burner and fabric 5. Flame width Singeing parameters
  18. 18. 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
  19. 19. 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
  20. 20. 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
  21. 21. Pre-requisite for singeing • Full dry fabric Fabric parameters to be considered for optimum singeing • Fabric construction • Fabric thickness • Heat sensitivity
  22. 22. 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
  23. 23. 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
  24. 24. 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
  25. 25. 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
  26. 26. 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
  27. 27. 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

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