Determination of Hole Blocking Conditions for Perforated Sifting Surfaces

The efficiency of widespread technological processes of sieve sifting of loose materials depends on timely cleaning of holes from the blocked particles. The blocking of holes occurs under specific conditions related to mechanical-and-physical properties of loose material particles, constructive and technological parameters of perforated sifting surfaces and clean-up systems. We established the conditions that contribute to blocking of holes of sifting surfaces and identified all significant factors, namely size, mass, constant of friction and Young's modulus for loose material particles; form and size of hole, thickness of perforated surface; loose material layer thickness and velocity. Using analytical and experimental methods, we identified variation range of these factors for loose material particles of biological origin, such as buckwheat, wheat, peas, corn. As a result of this study, we received analytical equations for determination of force of adhesion of loose materials particles with the edge of holes of perforated surfaces. The numeric calculations allowed establishing the dependence of the force of adhesion on moisture and thickness of loose material layer, as well as thickness and shape of the holes of the perforated surfaces. We have also established the dependence of constant of friction, mass, Young's modulus from the moisture of particles of loose material. The obtained results make it possible to determine the force of adhesion and prediction the power necessary for unblocking this hole, created by the cleaning system elements, such as brushes and elastic impact cleaners. The use of this method will make it possible to justify the parameters of the system for cleaning holes of perforated sifting surfaces with different types of holes and when separating different types of loose materials.