The phenomenon of screen blocking for mixtures of varying blocking grain content

Abstract

Article is devoted to sieve holes blocking and describes the impact of the content of blocking grains in the feed on this phenomenon. The process of screen blocking involves grains of varying size being blocked in sieve holes. this is a phenomenon that significantly decreases the screening process capacity. the screen blocking coefficient f is applied for a description of screen blocking. Blocking grains are the ones which is equal to or slightly larger than the sieve holes. Those grains do not pass through the sieve holes, remain over the sieve and may clog (block) the sieve holes, thus reducing the screen clearance coefficient. the tests were done using a laboratory vibrator and control sieves, by subsequently screening mixtures of particulate materials with a different content of blocking grains and different percentage share of the upperand lower-size fractions. Particulate materials of three model grain shapes were used for the tests: spherical, sharp-edged and irregular. The paper also includes a statistical analysis of the results obtained through experiments and an innovative method for describing sieve holes blocking. the new blocking coefficient specifies the percentage number of blocked sieve holes in relation to the total number of sieve holes. grain size is a parameter that determines the value of the screen blocking coefficient in time. an increase in the content of blocking grains in the mixtures results in an increase in the percentage number of blocked sieve holes. the content of individual fractions in the mixture also has a significant impact on the course of sieve holes blocking. screening is a very common industrial practice, and various designs of screens and types of sieves are available. that is why the subject of this paper is so important.