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  • QA 023
    Question:
    Does one need both a grader and a gravity table in a small milling line?
    Background:
    We are planning to install a small coffee milling line. One supplier insists on both a grader and a gravity table - another suggests just the gravity table will do.
    Asked by:
    Exporter - Haiti
     
    Answer:

    Your choice will depend to a certain extent on the type of coffee you intend processing and exporting. Chapter 11 of the Guide (11.05.08 - beansize, and 11.05.09 - bean density) explains the functions of graders, catadors and gravity tables.

    If you dispense with the size grader then, obviously, you will not be able to grade coffee accurately on size, only on density. However, when correctly operated the gravity table does separate coffee by size in the sense that heavier  beans usually are larger as well. But it would be difficult to maintain consistency.

    Size separation on a gravity table cannot match the accuracy of a size grader and it is because of this that most modern milling lines indeed use the sequence 'size grader - gravity table'.

    This assumes that the milling operation takes care of the initial separation of chaff and brokens, probably using a type of catador.

    Posted 1 June 2005

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