GAS singeing process monitoring & control

An indicator of the singeing effect is the fabric temperature just after its passing over the singeing flame. The fabric temperature can be continuously monitored by a radiation pyrometer and indicated by a thermometer. Hence, the fabric temperature may take over the singeing control and regulating function. When the fabric temperature increases to a pre-set value, the machine intensity would automatically reduce, while when the fabric temperature goes down, the flame intensity would automatically increase.

Hairiness Tester provides another possibility to control the singeing effect objectively. The fabric surface is monitored by means of a laser beam and the hairiness of the fabric is displayed on a computer screen. The measured information can be used as a set value for the control of the singer in order to achieve the programmed effect.

Important considerations during GAS singeing

• Make sure that the flame is more bluish (less yellowish) to give the maximum temperature.
• Control and maintain the recommended flame length and angle of contact, depending on the fabric construction, thickness, weight, heat sensitivity, etc.
• Regulate the fabric speed according to the fabric construction/thickness/weight etc.
• Make sure that all the burner nozzles are free from choking. Choking of nozzles may result in the appearance of haziness, patchy appearance or faint lines, which become apparent after dyeing.
• Make sure that the machine is threaded through the machine correctly. Rubbing marks may show up if the fabric is threaded wrongly over defective stationery bars and/or if the fabric rubs against the burners. (As the guide rollers are very close to the burners, any problems due to loose brackets supporting the rollers will guide the fabric to touch the burner block/nozzle). Invariably such defects only show up after dyeing or finishing, at which stage it is difficult to attribute the cause to the singeing machine operation.
• Make sure that the threading is as per specification drawing so that both sides of the fabric are singed. Singeing on only one side of the fabric may result in face to back shade variation after dyeing.
• Make sure that the width of the flame is set to cover just a little more than the fabric width. This will ensure conservation of energy.
• Make sure that the exhaust blowers over the burners are in proper operation. If not, it can lead to re-deposition of the burnt out fibres on the fabric causing black specks.
• Ensure appropriate quenching into water/desize bath after singeing. Otherwise, the entrapped smouldering particles may lead to fabric getting burnt (holes).
• Guide rolls next to the flames or the guide rollers on which flame is directed in case of heat-sensitive fabrics should be cooled, generally by cold water circulating through the guide rollers. Otherwise they could become red hot and scorch the fabric.
• Interlinking of stop button/flame switch-off mechanism/ quenching system should be effective to avoid burning of the fabric and any incident of fire.

Testing singeing effectiveness

The effectiveness of singeing process can be checked by one or more of the following:

• By looking at the singed fabric with magnifying glass and comparing its hairiness with that of the un-singed fabric. A well-singed fabric shows less hairiness.
• By testing the singed fabric for pilling performance and comparing it with that of the un-singed fabric. A well-singed fabric gives less pilling.
• By sticking and removing a sticking tape on the singed fabric and observing the number of fibres attached to the sticking side of the tape. A well-singed fabric results in less number of fibres sticking on the tape.
• Noticing the feel or handle of the singed fabric. An over-singed fabric may give a harsher feeling.