content and amount of foreign material present, increasing with an increase in either. The tangent of this angle is recognized as the coefficient of friction of the material on itself.
This property is important in material transfer since it affects the capacity of belt conveyors and other bulk transfer devices and partially determines the minimum slope of floors in self-emptying bins, coefficient of friction of grain on the bin material being another factor. Some materials, particularly those that have been produced by grinding, have such steep repose angles that they are not completely self-flowing. Agitation is usually necessary to maintain flow