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  • 2.1.9-COTTON VALUE ADDITION-GIN STANDS

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  • Gin stands

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

     
     

    The saw gin was developed by Eli Whitney in 1793. In a gin stand, round saws rotate at a high speed between parallel metal bands called ribs. Saw gin stands typically have 12–18" (30.5–45.7 cm) diameter saws spaced 1/2–1" apart, with as many as 198 saws stacked on a single mandrel. These saws projects through the ginning ribs, grasp fibre, and pull the fibre from the seed as the seeds are too large to pass through the opening in the ginning ribs. The capacity of a single gin stand has increased from less than 1 bale per hour to more than 15.

     

    The fibre–seed attachment force varies with cotton variety, field deterioration, moisture content and other factors, but is typically about 55% of the breaking force, suggesting that the fibres can be removed from the seed without breakage. The gin stand, whether saw (see figure 2.7) or roller, pulls the fibre from the seed. It is the heart of the ginning system. The capacity of the system and the quality and potential spinning performance of the lint depend on the operating condition and adjustment of the gin stand. Gin stands must be properly adjusted, kept in good condition, and operated at or below design capacity. If gin stands are overloaded, the quality of the cotton may be reduced. Short fibre content increases if the ginning rate increases above the manufacturer’s recommendation. Short fibre also increases as saw speed increases. Increased ginning rate also increases yarn imperfections, and seed damage can result from increasing the ginning rate, especially when the seeds are dry. High ginning rate and low seed moisture cause seed damage ranging from 2% to 8% of the seed in gin stands. Thus, it is paramount to keep the gin stand in good mechanical condition, to gin at recommended moisture levels, and to not exceed the capacity of the gin stand or other components of the system.

    Figure 2.7: Continental Eagle 161 Golden Eagle Saw brush-type gin stand2.1.9-en