Facts & Figures Book - KPI-JCI

. Lump size and the percentage of fines can have amajor effect on width selection. As a rule of thumb, for a20-degree surcharge angle, with 10 percent lumps and90 percent fines, the recommended maximum lump sizeis one third of the belt width (BW/3). With all lumps and nofines, the recommended maximum lump size is one fifth ofthe belt width (BW/5). For a 30-degree surcharge angle,with 10 percent lumps and 90 percent fines, the recommendedmaximum lump size is one sixth of the belt width(BW/6). With all lumps and no fines, the recommendedmaximum lump size is one tenth of the belt width (BW/10).Belts must be wide enough so any combination of lumpsand fine material do not load the lumps too close to theedge of the belt.c. The cross section of how the material settles on a movingbelt can have a major effect on expected tonnage for agiven width conveyor.Material HandlingFACTORS AFFECTING THE CROSS SECTION ARE:• The angle of repose of a material is the angle that thesurface of a normal, freely formed pile, makes to thehorizontal.• The angle of surcharge of a material is the angle tothe horizontal that the surface of the material assumeswhile the material is at rest on a moving conveyor belt.This angle usually is 5° to 15° less than the angle ofrepose, though in some materials it may be as muchas 20° less.• The flowability of a material, as measured by itsangle of repose and angle of surcharge, determinesthe cross-section of the material load that safely canbe carried on a belt. It also is an index of the safeangle of incline of the belt conveyor. The flowabilityis determined by such material characteristics as sizeand shape of the fine particles and lumps, roughnessor smoothness of the surface of the material particles,proportion of fines and lumps present, and moisturecontent of material.190