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  • 2.7.2-COTTON VALUE ADDITION-BALE STRAPPING OR BANDING MATERIALS

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  • Bale strapping or banding materials

    Chapter 2 - Cotton value addition - Cotton bale packaging

     
     
    Bale banding materials are typically constructed of steel bands, high tensile steel wire ties or plastic (polyethylene terephthalate) bands. It is especially critical that bale banding materials be strong enough to withstand the static loads containing the fibres in bales as well as impact forces of handling. Broken bands can represent a significant risk because of probable loss of fibre weight, inefficient handling, and contamination potential.

    Cotton bales are formed under high compression; therefore high-strength bands must be used to restrain bales at the desired dimension. Typically, bands may have a strength capacity of up to 9,000 N per band. While the average static bale forces may be as low as 4,000–5,000Nper band, an additional safety margin is required to compensate for dynamic forces created during storage, handling and transport. Heavy bales can create much higher bale strapping forces than bales of average weight. Research has shown bale forces increase exponentially with increases in density; therefore, in a bale having a fixed length band, density increases in proportion to its weight increase. Similarly, a bale which may be formed with varying distribution of lint across its cross section is also subject to band breakage. Ginners usually discover quickly if lint distribution is a problem and make corrective adjustments before significant problems arise. Temperature and humidity changes also affect internal bale forces. Moisture conditions for the cotton fibre during compression are a significant factor: the lower the moisture content, the higher the force on the bale bands.

    Optimum banding specifications, like bale size and density, represent a compromise of attributes. Steel bands having high load-carrying capacity are less likely to break than plastic bands under a given load. On the other hand, plastic bands allow elongation, relieving compressive static forces from the fibres, which in some cases actually decreases breakage. Steel is stronger than plastic at elevated temperatures, as may occur near a fire. Proper fire protection measures including sprinklers are recommended for all storage areas.

    Steel bands are more difficult to remove in the opening room of the textile mill. Many mill opening room personnel prefer the ease of removal of plastic bands. While personal safety equipment to protect eyes, limbs and body from the forces of breaking bands is recommended for all bales, the risk of injury from removing plastic bands is considered to be less than that for steel. The arrangement of the strapping inside the protective wrapping material permits automatic opening of the bales by machine provided that the hoops are parallel.

    United States specifications for bale packaging materials have been carefully researched and have been established to include sufficient safety factors to compensate for all except the most unusual circumstances. United States standards for bale banding materials are being widely adopted in many cotton growing areas of the world.