Influence of the mechanical characteristics of harp screen material on screening process

Abstract

The paper presents the results of studies on the influence of mechanical characteristics of harp screen material on the technological  parameters of screening. A mathematical model of the vibrational  process of harp screens is presented depending on the length of their  free areas, magnitude of technological load and characteristics of the screened material. Dependences of the relative vibrations amplitudes  of rubber and cable strips on the length of their free areas are determined for different values of process load. As a result of the researches, it was established that the amplitude of the relative vibration of  rubber strip under load decreases with increasing length of their free  areas and for steel cable strips it increases, reaching a maximum at  certain values of process load. It was also found that presence of the  load dramatically reduces the amplitude of relative vibration of rubber  strips, especially, in the area of dimensionless frequencies of the order of (0.6  –  1.4)g, while the vibrations amplitude of cable strips vary  slightly in this frequency range. The article presents information on  rubber-cable harp screening surfaces of mesh type: strips in the form  of steel cables, rubberized with rubber cover having lateral separation  projections. The use of rubber-cable strips as working elements of the  screening surface allows to increase the “open area” of the screen due  to the increase of distance between supports while maintaining high  and stable amplitude of strips vibrations. Optimization of mechanical characteristics of the working elements material of harp screens and  conditions of their fixation allows to intensify separation of screened  material into fractions by eliminating sticking of the screened surface  with clay particles and clogging of the material with “difficult” grains, and to improve significantly technical and economic indicators of the  screening process. Such screening surface passed successful industrial tests at a number of quarries producing construction aggregates for the separation of crushed stone and gravel. Economic efficiency of the rubber-cable harp screens is presented in comparison with the wire screens in technological schemes of processing of mineral raw materials.