slope, hanger angle as well as the friction between
particles and screen is parameters that should be
considered for effective screen sizing. Grain size
determination is important in the design of screen
opening [12]. Grains are best assumed spherical and
their spherical mean can be obtained by taking
geometric mean of their mutually perpendicular axes
and sphericity is the percentage of ratio of the
spherical mean and the major diameter [13]. When
the value of sphericity is greater than 85 %, circular
shaped sieves is sufficient for final separation while
those that within 32 to 50 % require an oblong shaped
sieve [14]. Optimum tilt angle of sieves for a cereal
cleaner occurred between 4 and 5° when operating
between 300 and 350 rpm with a cleaning efficiency of
61 % [6].