Arnot Sorter
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Modern methods of sorting were introduced along with mechanisation in the 1870s. Mechanical sorters were developed to utilize power from steam engines and other sources. In 1880.
More modern sorting machines incorporate different sieves with meshes of size 8,10,12,16,24,30 or greater. Tea passed over a number 8 mesh is cut and sifted again, and so on. As the tea passes through the various meshes, it is classified into grades such as whole leaves, broken leaves, fanning, and dusts.
In modern factories a Myddleton machine is used at the first stage of the operation for orthodox teas. For CTC manufacture, an electrostatic stalk extraction unit is used first. Usually, in orthodox manufacture, the spillover from the Myddleton is passed through a ghugi or rotary hexagonal sifter; from the trays, the leaf is passed into the Arnott and Macintosh sorters. But in CTC and leggcut manufacture, the ghugi is not used. Thereafter, the process incorporates the Britannia Tea Sorter (which works very well in duel manufacture), the Macintosh sorter and the wind tunnel. A number of hand sievings are also essential to produce some quality grades. In wind tunnels and waterfalls, fibre and dust grades are separated according to the specific gravity of the particle. Tea breakers and cutters are extensively used in modern sorting operations to reduce particle sizes for subsequent classification.
In orthodox manufacture, the first classification of tea takes place at the time of sifting. BOP, BOPF and OP grades are produced from the first and second fine teas. The coarse leaf that is first broken or cut goes into the production of BP, PF and souchong grades. In CTC and leggcut manufacture, sorting is based wholly on the size of the leaf particles