bond work index formulaequationthe basic work index equation is: w = 10 wi/p 10 wi/f(1) where w is the work input required in kilowatt hours per short ton to grind from 80% passing f microns to 80% passing p microns, and wi is the work index, or the grinding resistance parameter. it represents the energy input required in kilowatt hours to reduce a short ton from theoretically infinite feed size to 80% passing 100 microns. this simple equation has been extremely useful in analyzing and grinding operations, and in predicting the performance of new installations. it can be written in the following form: wi = w/(10/p 10f)..(1a) the work index wi can be determined from plant operations and from laboratory ball mill grindability, rod mill grindability, and impact crushing tests. the laboratory test results are used to check the efficiency of commercial operations and to compute the proper machine sizes for new installations. in the standard ac closed circuit b see full list on 911metallurgist the trend of the particle size distribution line is shown by plotting its screen analysis in, such a manner that a complete homogeneous crushed or ground product will form a straight lineany curvature then indicates a natural or induced grain size. semilog paper is used with the percent cumulative retained plotted on the vertical logarithmic scale y. straight lines which each represent one mesh sieve size of p1 microns are drawn radiating from the upper left hand corner of the ploteach crosses the 20% retained, or 80% passing, line at w = 10/p1 where w is the horizontal lineal x value at y = 20. the total work input to the sample in kwh/ton divided by the work index wi is w. the straight plotted distribution line follows the exponential equation: ax = log b log y.(5) where b is the y intercept of the extended line, and a is the negative slope. the 80% passing size p is 100/w² microns. the exposure ratio er is the quantity that expresses the lin see full list on 911metallurgist in a recent publication fifteen different ores each had grindability tests made at 28, 35, 48, 65 and 100 mesh, with many work index variations at the different product sizes. these tests are used here to develop empirical equations from which the work index at different product sizes can be computed from a grindability test at one size. in each of the 15 ores the data from the grindability test at 48 mesh alone were used to calculate the wi values at 28, 35, 65, and 100 mesh, and these were compared with the actual values obtained by testing. in the calculation the exposure ratio erp of each mesh product size was considered to be that determined by testing at 48 mesh, and crp was determined from that value and the average p for each mesh size. the work index should theoretically be proportional to (crp crf) p/yn where y is the percent weight of the feed retained on the mesh size tested. from this relationship wi = k (crp crf) p/y 1.67..(7) the exponent see full list on 911metallurgist the specific crack length cr100 in centimeters per cc of solid for any material ground to 80% passing 100 microns with an exposure ratio er is found from: cr100 = log (er + 0.28) + 0.77/0.0125(14) since joules (watt seconds) per gram equals 3.97 times kwh/ short ton, the crack energy ce in joules per centimeter is found from: ce = 3.97 wi100 sg/cr100.(15) where sg is the specific gravity. combining eq. (14) and eq. (15) gives the following equation for calculating the crack energy in joules per centimeter directly from the standard work index and product exposure ratio: ce = .0496 wi100 sg/log (erp + 0.28) + 0.77.(16) from eq. (16) and table i, the ores tested (with an average specific gravity of 2.86) have an average crack energy of 4.0 joules per centimeter. since the work input varies as the crack length, or as the square root of the surface area, surface areas should not be used in computing the work required for see full list on 911metallurgist linknovate kinetic grinding test approach to estimate the the standard bond method is a tedious time consuming procedure requiring at least 710 grinding cycles, so that many researchers have tried to simplify this method to be able to perform a rapid calculation of a work index. (pdf) a quick method for bond work index approximate value in this work, the energy and exergy analyses of a cement ball mill (cbm) were performed and some measurements were carried out in an existing cbm in a cement plant to improve the efficiency of the 3bond work index an overview sciencedirect topicsthe ball mill work index laboratory test is conducted by grinding an ore sample prepared to 100% passing 3.36 mm (6 mesh) to product size in the range of 45150 µm (325100 mesh), thus determining the ball mill work index (wib or bwi). application of operating work indices in autogenous work indices for the ag/sag mill and ball mill can be reorganised as  and , where bwio and awio are the corrected operating work indices and wag/sag, wbm are the respective power draw of ag/sag and ball mills. note that the ball mill operating work index is applied only on the portion that needs the additional grinding (q2), 309kb 4ball mill design/power calculationdec 12, 2016 · ball mill power calculation example a wet grinding ball mill in closed circuit is to be fed 100 tph of a material with a work index of 15 and a size distribution of 80% passing ¼ inch (6350
amit 135: lesson 7 ball mills ampcircuits mining mill for overflow ball mills, the charge should not exceed 45% of the mill volume . for grate discharge mills, the charge should occupy about 50% of the mill volume . bond developed a relationship that can be used to determine the percent charge by volume as a function of the vertical height above the charge, he, and the radius of the mill, r, i.e., ball mill design/power calculationdec 12, 2016 · ball mill power calculation example a wet grinding ball mill in closed circuit is to be fed 100 tph of a material with a work index of 15 and a size distribution of 80% passing ¼ inch (6350 microns). ball mill operatng work index calculationball mill operatng work index calculation bryan d. hellmann work index spreadsheet was designed to estimate the operational work index of a given grinding installation of known dimensions and operating conditions of the operational response of conventional ball mills in various grinding circuits. bond work index procedure and methodsep 22, 2017 · this grindability test or bond ball mill work index procedure is used to determine the bond work index of minus six mesh or finer feed ore samples. these equation application methods are used to process <1/2 ore samples in a ball mill using a standard ball charge. operating work index is not the specific energy consumptionoct 24, 2018 · the work index can either be measured in the laboratory (the bond ball mill work index determination is a common example) or it can be calculated from the operating performance of a milling ball mill work index calculationcalculation of energy required for grinding in a ball,a bond ball mill work index is then performed on the mill product for the design of sagball mill circuits this is important because it was found that there was a 115 kwht higher ball mill work index if the 335 mm ball mill test feed size is moret.get price o. i. skarin n. o. tikhonov calculation of the required work index rwifor finer particles ball milling work index bwi (table). these indexes are readily obtained using the specialpurpose laboratory equipment (fig. 1). finding the total specific energy consumption in the wet autogenous mill central discharge ball mill circuit (wam cdbm) in the framework of the discussed method, total
kinetic grinding test approach to estimate the ball mill work ball mill work index test was widely used in the 1960s and still remains in use today (gharehgheshlagh 2016). the ball mill work index of the feed samples was determined according to the standard 20150505 bond efficiencygmgicev1r04 determining the bond wioact actual operating bond work index determined from measurements on the circuit (kwh/t) wirm bond rod mill test work index (kwh/t) wistd standard circuit bond work index (expected or designed) used for circuit design. specific energy requirement at the drive pinions. 3.keywords work index, work index efficiency, bond work index testing general work input function for sizing grinding ball mills equations for power draft, capacity and work input for predicting the performance of industrial grinding mills are derived based on torque measurements using a laboratory instrumented mill. these derivations are based on mechanical principles and on the firstorder kinetics of the grinding process. rittingers, kicks and bonds laws express work input as work index (wi) times a particle how to size a ball mill design calculator ampformulaapr 08, 2018 · the parameter wi, known as the work index of the ore, is obtained from batch bench tests first devised by bond (1961). the power calculated on using equation 1, (bond, 1961rowland and kjos, 1978), relates to: 1) rod milling a rod mill with a diameter of 2.44 meters, inside new liners, grinding wet in open circuit. modeling the specific grinding energy and ballmill scaleupzthe ballmill power drawp as a function of its dimensions: internal mill diameter d and length l, zthe ballmill power drawp as a function of the feed d f (mm) and the product size d (mm), the bond work index w i (kwh/short ton) and the mill throughput t (short ton/h), zthe ballmill dimensions (d and l), when not only d f, d, w ball mill design/power calculationapr 08, 2018 · ball mill power calculation example 1 a wet grinding ball mill in closed circuit is to be fed 100 tph of a material with a work index of 15 and a size distribution of 80% passing ¼ inch (6350 microns). the required product size distribution is to be 80% passing 100 mesh (149 microns).