• Effect of gin machinery on cotton quality

    Chapter 2 - Cotton value addition - Impact of varieties and production practices 


    Good gin operations use only the amount of drying, moisture restoration and cleaning required to meet customer demands. New, proven technology must be used to process cotton as well as to monitor and control fibre quality.

    The ginning process can significantly affect fibre length, uniformity, and the content of seedcoat fragments, trash, short fibres and neps. The two ginning practices that have the most effect on quality are the regulation of fibre moisture during ginning and cleaning, and the degree of gin cleaning used. Figure 2.9 illustrates the impact of moisture on fibre quality. The addition of seed cotton cleaning machinery affects some fibre quality parameters, and saw-type lint cleaners affect nearly all fibre quality parameters. Large and small trash particles are removed by gin machinery. Particles commonly known as ‘pepper trash’, which are typically about 500 microns, are dramatically reduced by all gin processes except gin stands. Saw-type lint cleaners are especially efficient at removing small trash particles.

    Figure 2.9: Moisture content during gin processing is a compromise between cleaning efficiency and fibre quality



    Choosing the degree of gin cleaning is a compromise between fibre trash content and fibre quality. Lint cleaners are much more effective in reducing the lint trash content than are seed cotton cleaners, but lint cleaners can also decrease fibre quality and reduce bale weight (turnout) by discarding some good fibre with the waste. Cleaning does little to change the true colour of the fibre, but combing the fibres and removing trash and dust changes the perceived colour. Lint cleaning can sometimes blend fibre so that fewer bales are classified as spotted or light spotted. Ginning does not affect fineness and maturity although these properties affect the amount of damage to lint during ginning and lint cleaning. Each mechanical or pneumatic device used during cleaning and ginning increases the nep content, but lint cleaners have the most pronounced influence. The number of seedcoat fragments in ginned lint is affected by the seed condition and ginning action. Yarn strength, yarn appearance and spinning-end breakage are three important spinning quality elements. All are affected by length uniformity and, therefore, by the proportion of short or broken fibres. These three elements are usually best preserved when cotton is ginned with minimum use of drying and cleaning machinery.

    Compared to saw ginning, roller ginning has a higher turnout and produces lint that is longer, with fewer short fibres and neps, but contains more foreign matter and cottonseed. The roller gin process results in a lint appearance that is less smooth than that of saw-ginned lint.

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    Cotton Exporter's Guide

    Brochure - African cotton promotion
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