The section where the supplied compressed bale is turn into a uniform lap of particular length by opening, cleaning, blending or mixing is called blowroom section. It is the first steps of spinning.
The main tasks of blowroom process are opening, cleaning, and blending of cotton fiber tufts without overstressing of fibers. One important function of the blow room is to disintegrate the fiber bales into a flow of very small clumps of fiber, which are sufficiently small in size to be digested by the cards. About 40%–70% trash is removed in the blow room section.
Blow room line consists of different machines and each manufacturer provides its own line of machines. The sequence of machines in a typical blow room line is shown in the Figure 1. Blowroom starts on the left with a bale breaker, followed by several cleaning units and a mixer, and is completed with a dust and foreign matter extractor. The next step is carding.
In the latest blow room lines, the material from fine opners / cleaners is transferred to the card directly by a fan through a chute feed system which is attached at the back of the card. Figure 2 shows the latest blow room line in which the scutcher is excluded and fine cleaner delivery pipes are directly connected to the cards.
The sequence of machinery arrangement in the blow room process for a particular process depends on the following factors:
- Fiber type
- Fiber characteristics
- Trash content
- Material throughput
- Mixing formulation
Objectives of Blowroom Section:
Objectives of a blowroom line are as follows:
- Opening: To open the compressed fibers up to very small tufts
- Cleaning: To remove the impurities like seed fragments, stem pieces, leaf particles, neps, short fibers, dust and sand
- Mixing and blending: To make homogenous mixture of the material
- De-dusting: To extract the dust if present
- Uniform feed for card: To convert the mass of fibers into thick sheet called lap which should be uniform length and width wise or to provide output in the form of tufts of optimum size
Functions and Operations in Blowroom Section:
- Dust Removal
- Mixing and Blending
- Even feed of material to the card
The first operation required in the blowroom line is opening, carried out to the stage of tufts – in contrast to the cards, where it is performed to the stage of individual fibers. Tuft weight can be reduced to about 0,1 mg in the blowroom. The small improvements by each of the subsequent machines are obtained only by considerable additional effort, stressing of the material, unnecessary fiber loss and a striking increase in neppiness. If necessary the card is able to assume rather more of the overall task.
Bale opening consists of opening the bales and converting them into single-fiber flocks. The type and intensity of the individualization of the fibers critically influence the further processing steps. The more intensively the cotton fibers have been individualized, the more contamination particles appear on the surface of the fiber bulk and may be removed. Target weights for the individualized flocks are about 0.02 to 0.03 gm.
With modern bale-reducing systems, up to 80 bales are lined up on the floor and reduced by a programmable bale breaker in layers from top to bottom. Fiber flocks are removed mechanically with the help of beaters (Figure 3). The fiber flocks are then transported by air streams through pipelines.
The main functions of the opening and cleaning machines are the further separation of the fiber flocks and the removal of contamination particles and dust from the cotton. High fiber throughput with as little fiber damage as possible is desired.
It has to be kept in mind that impurities can only be eliminated from surfaces of tufts. Within a progressive line of machines it is therefore necessary to create new surfaces continuously by opening the material. And even then the best blowroom line is not able to eliminate all, or even almost all, of the foreign matter in the raw material. A blowroom installation removes approximately 40 – 70% of the impurities. The result is dependent on the raw material, the machines and the environmental conditions.
It is clear from this diagram that the cleaning effect cannot and should not be the same for all impurity levels, since it is easier to remove a high percentage of dirt from a highly contaminated material than from a less contaminated one. Looking at the machine, the cleaning effect is a matter of adjustment. Increasing the degree of cleaning also increases the negative effect on cotton when trying to improve cleaning by intensifying the operation, and this occurs mostly exponentially. Therefore each machine in the line has an optimum range of treatment. It is essential to know this range and to operate within it.
In an investigation saw that the quantity of waste eliminated on a cleaning machine by modifying settings and speeds was raised from 0.6% to 1.2%: while the quantity of foreign matter eliminated increased by only 41%, the quantity of fibers eliminated increased by 240%. Normally, fibers represent about 40 – 60% of blowroom waste. Thus, in order to clean, it is necessary to eliminate about as much fibers as foreign material. Since the proportion of fibers in waste differs from one machine to another, and can be strongly influenced, the fiber loss at each machine should be known. It can be expressed as a percentage of good fiber loss in relation to total material eliminated, i.e. in cleaning efficiency (CE):
AT = total waste (%); AF = good fibers eliminated (%).
For example, if AT = 2.1% and AF = 0.65%:
C. Dust removal:
Almost all manufacturers of blowroom machinery now offer dust-removing machines or equipment in addition to opening and cleaning machines. However, dust removal is not an easy operation, since the dust particles are completely enclosed within the flocks and hence are held back during suction (because the surrounding fibers act as a filter). Since, as shown it is mainly the suction units that remove dust (in this example 64%), dust removal will be more intensive the smaller the tufts.
It follows that dust elimination takes place at all stages of the spinning process.
D. Mixing and blending:
Blending of fiber material is an essential preliminary in the production of a yarn. Fibers can be blended at various stages of the process. These possibilities should always be fully exploited, for example by Transverse doubling transverse doubling. However, the start of the process is one of the most important stages for blending, since the individual components are still separately available and therefore can be metered exactly and without dependence upon random effects. A well-assembled bale layout and even (and as far as possible simultaneous) extraction of fibers from all bales is therefore of the utmost importance. Simultaneous extraction from all bales, which used to be normal in conventional blending batteries, is now no longer possible (automatic bale openers). Accordingly, intensive blending in a suitable blending machine must be carried out after separate tuft extraction from individual bales of the layout. This blending operation must collect the bunches of fibers arriving sequentially from individual bales and mix them thorough.
The consistency in yarn quality depends heavily on the homogeneity of the material composition. The objective of mixing and blending is to optimize the homogeneity of the material mixture by combining several bales.
Further objectives of mixing and blending are:
- Decrease in irregularities in bales of different origins,
- Economic processing,
- Recycling of comber waste and other offal,
- Improved properties of the final product, and
- Reduction of raw material costs.
E. Even Feed of Material to the Card:
Finally, the blowroom must ensure that raw material is evenly delivered to the cards. Previously, this was carried out by means of precisely weighed laps from the scutcher, but automatic tuft feeding installations are used nowadays. While in the introductory phase such installations were subject to problems regarding evenness of tuft delivery, today they generally operate well.
Lap Forming System:
To convert the opened and cleaned fibers into a sheet of particular width with uniform weight/unit length is called lap. The Lap so formed is wound on the lap spindle to make it suitable for the next process of carding.
Chute Feed System:
In case of chute feed system instead of forming blow room lap, the opened, cleaned, mixed/blended material is fed to the carding machines through pipe line in tuft (sheet form) by the action of air.
- Textile Engineering – An Introduction Edited by Yasir Nawab
- Textile Technology: An Introduction, Second Edition by Thomas Gries, Dieter Veit, and Burkhard Wulfhorst
- Process Management in Spinning by R. Senthil Kumar
- Process Control and Yarn Quality in Spinning By G. Thilagavathi, and T. Karthik
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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.