Defects in Blow Room: Causes and Preventive Action

Last Updated on 11/10/2022

Blowroom is the initial stage in spinning process. Opening, cleaning, blending or mixing is done here. As a result different defects occur in different operation of blow room. Basically, many of the following defects are related with lap forming process associated with conventional blow room. In modern blow room line, the material from last machine in the blow room sequence is directly fed through chute to the Card. Major defects or faults in blow room are mentioned below.

Defects in Blow Room

List of Faults / Defects in Blow Room:

  1. Uneven lap
  2. Irregular lap
  3. Soft lap or bulged laps
  4. Conical lap or Barrel shape laps
  5. Stringy Laps
  6. Licking lap
  7. Heavy or light laps
  8. Split lap
  9. Dirty lap
  10. Rich Droppings
  11. Defective Lap Edges
  12. Holes in Lap
  13. Patchy lap
  14. Ragged lap selvedge

Causes for Defects in Blow Room:
Important causes for defects in blow room are given below:

1. Causes for uneven lap:

  • Uneven feeding of cotton.
  • Faulty working of feed regulating mechanism.
  • Shifting of belt over the cone drums not smoothly taking place – either the belt has become too stiff (not pliable) or it has not been pieced-up properly. A belt strap wider in width is not sensitive enough to bring about the changes sensed and conveyed by the regulating mechanism.
  • Uneven loading on the feed roller and improper alignment of the feed roller with the beater – allow uneven snatching of fibers. The slippage of pedal roller causes uneven delivery of material.
  • Feed lattice slipping over its driving shell.
  • Too low fan speed – Easy and smooth withdrawal of the material through the beater zone not allowed. The air turbulence due to dirty flue pipes and cages affects uniform distribution of cotton on cages.

2. Causes for nep formation in blow room:

  • Cotton with too high or low moisture.
  • Extremely fine cottons with high trash content.
  • Reprocessing of laps and mixing of soft waste.
  • Rough or blunt blades and bent pins on beaters.
  • Narrow settings between the feed roller or pedal and beater.
  • Long curved and U-bends in conveyor pipe lines.
  • Inappropriate ratio of fan to beater speed.
  • Wider setting between stripping rail and beater blade.

3. Stringy laps:
Overbeating action of some of the beaters in blow room curls the fibres. A tuft of fibres that is repeatedly beaten up by the beater blades tends to form ‘strings’. With heavier beating, the string size also grows. Once formed, the strings are very difficult to open out in subsequent processes and may cause difficulties in drafting process.

The possible causes / reasons are:

  • Too high beater speed
  • Too low fan speed and
  • Excessive moisture in the cotton processed.

4. Causes for curly cotton:

  • Grid bars setting too close to beater.
  • Hooked or bent pins on kirschner beater.
  • Too wide a setting of stripping rail.
  • Long and bent conveyor ducts with low fan speed.

5. Causes for dirty laps:

  • The laps contain substantial amount of visible impurities and thus appear dirty. This indicates poor cleaning in blow room.
  • Grid bars are too close to each other. They are required to be partially open for the liberated trash to fall down through them.
  • Excessive fan speed preventing cotton from being adequately cleaned in the beater zone.
  • Beater speed is comparatively slower, causing ineffective cleaning action.
  • Setting between the beater blades and the pedal roller too wide, thus causing lumps of cotton being snatched.
  • The mild air currents returning back into beater chamber through the grid bar causing the trash to return back into beater zone – recombination of lint and trash within the beater.

6. Heavy or light laps:
The possible reasons are improper feed due to:

  • Photo cell/sensor problems, improper functioning of feed regulating motion in scutcher like improper shifting of cone drum belt, improper shifting of discs in PIV drive.
  • Worn out parts in feed regulating motion like links, cone drum belts, PIV chain, cone drum bearing, etc.
  • Improper synchronization of back machines.

Check lever movement and fulcrum and adjust the same. Stop the scutcher and restart it only after all reserve boxes and chambers in mixing are full.

7. Causes for lap Licking:

  • Use of too much soft waste in mixing
  • Too high fan speed, excessive beating.
  • Cotton is damp or departmental humidity is high.
  • Sticky nature of material

8. Rich droppings:
It means that there is considerable proportion of lint or fibrous matter in the droppings under the beater. The possible causes are –

  • Excessive amount of soft waste in mixing.
  • Grid bars set either too deeply and/or are more open.
  • Air suction of the fan too weak, thus allowing cotton to linger in the beater chamber.
  • Excessive beater speed leading to more forceful action on the material being processed.

9. Causes for conical lap or barrel shape lap:

  • Improper functioning of pedals on one side due to pedals being choked with dirt.
  • Air entering at one side from under the grid bar of beater.
  • Defective beater blade at one side.
  • Uneven suction at the cages leaving to deposition of more material on one side than another.
  • Lap roller racks, calander roller not exerting even pressure across the lap width. *Cages may not be properly levelled.

10. Causes for soft lap or bulged laps:
Inadequate calendar roller pressure due to wear and tear of weighting mechanism produces the soft lap.

11. Defective lap edges:
They usually occur due to accumulation of waste in the holes at the sides of the cages. This weakens the air suction on the sides of the cages, leading to irregular deposition. It leads to torn or ragged edges. Also, it is quite likely that some roughening on the inside surface of the passage that leads to cages cause intermittent deposition. An inspection can help in locating the roughenings. A periodic cleaning of the cages helps in preventing these blockages of the perforations on the cage.

12. Holes in lap:
Holes in the lap can be due to different reasons. Check the cages for damage, and reduce tension draft.

13. Patchy lap:
The unopened tuft results patchy lap. The various reasons for patchy lap are insufficient opening, improper setting between feed roller and beater, obstruction in cage, and poor suction in cage.

14. Ragged lap selvedge:
Ragged lap selvedges are mainly due to uneven spots at the edges. Check for the rough spots on the sides of the feed plates, leather linings for the cages, and keep the edges of the scutcher clean.

Preventive Action or Remedies of Faults in Blow Room:

1. Preventive action for neps formation:
For avoiding neps formation it is necessary to select the cotton according to moisture content in the cotton. In both cases if moisture content is less or more, our process will become critical.

As quality of our end product depends upon raw material. If cotton having more trash content then it is necessary to increase beating point. And this beating will directly affect our neps formation and neps formation will be more.

Cotton mixing supervisor should take action that during mixing soft waste and process lap not to be mix with fresh mixing. This step is necessary to avoid neps formation. As neps formation affect the quality of our yarn.

2. Preventive action for curly cotton:
For getting good quality product it is necessary to keep trained staff for maintenance point of view. There is a need of technical person who have full grip on their work. They should check the setting of machine and to keep machine update to avoid the problems. Machine setting must not be wide not so close to avoid curly cotton problem.

3. Preventive action for lap licking:
In order to prevent from lap licking it is necessary not to mix soft waste during mixing process. Avoid sticky nature cotton as in case sticky nature cotton then as a preventive action inside temperature of department is to be controlled. In this case low relative humidity and high temperature is needed.


  1. Process Management in Spinning by R. Senthil Kumar
  2. Principles of Spinning: Fibres and Blow Room Cotton Processing in Spinning By Ashok R. Khare
  3. Training and development of technical staff in textile industry by B. Purushothama
  4. Handbook on Cotton Spinning Industry by Purushothama

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  1. Blowroom: Objectives, Functions and Operations
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  3. Trutzschler Blow Room Line – An Overview
  4. Cotton Yarn Spinning Process Step by Step
  5. Neps in Carding: Major Defect in Yarn Manufacturing

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