Work index

Word processors Worker protection Work index Working fluids Work stations... 

A more practically useful work index based on empirical results from ball milling trials has been developed (7—9) and is expressed by equation 1 ... 

E Bond work index kWh/Mg (hp-hyton u Settling velocity of particles cm/s ft/s... 

E Work index of mill feed W Vector of differential size distribution ... 

Material Number tested Product diameter, im Work index E. Average abrasion index A,... 

The work index may be round experimentally from laboratoiy crushing and grinding tests or from commercial miU operations. Some rules of thumb for extrapolating the work index to conditions different from those measured are that for dry grinding the index must be increased by a factor of 1.34 over that measured in wet grinding for open-circuit operations another factor of 1.34 is required over that measured in closed circuit if the product size Xp is extrapolated below 70 [Lm, an additional correction factor is (10.3 + Xp)/l.l45X . Also for a jaw or gyratory crusher the work index may be estimated from... 

Material No. of tests Specific gravity Work index Material No. of tests Specific gravity Work index ... 

Nordberg Inc.—assumes feed weighing 100 Ib/fF and with a work index of 13. Range covered hy short-head and standard versions. 

W1 is Bond work index based on 100 percent passing a 200-mesh sieve, is the sohds feed rate in kg/min, and S is weight percent solids in the feed. This represents experimental data for limestone, feldspar, sulfide ore, and quartz. The influence of Wl is believed to be due to its effect on amount of fines present in the mill. Parameters that did not affect are specific gravity of feed material, and feed size over the narrow range studied. 

Grindabihty of phosphate rocks from different areas varies widely in Table 20-31 typical work-index data are shown. 

Rock type Calcium phosphate content, % Work index, kw.-hr./ton... 

The work index, Wjr is basically an indication of ore hardness, but also includes equipment efficiency. The Bond method has been the mainstay of size reduction circuit. It still holds a value, specially for initial design calculations, and for simple checks on efficiency. 

Ringertz, Nils. Alfred Nobel His Life and Work, Nobelprize.org. Available online. URL http //nobelprize.org/alfred nobel/ biographical/articles/life-work/index.html. Accessed on March 11,2008. 

Other Tests. The so-called tumbler tests are usually used for testing material like coke, coal, iron ore pellets or tablets. They can be divided into drum tests and ball mill type tests. The latter type is used to derive both the Hardgrove Index and the Bond s Work Index, which are often used to classify the material friability as described in Sec. 3. They are generally more suited to coarse material. The Hardgrove Grindability test requires an initial size range form 595 to 1190 microns. 

Bond terms Ei the work index, and expresses it as the amount of energy required to reduce unit mass of material from an infinite particle size to a size L2 of 100. im, that is q = 00. The size of material is taken as the size of the square hole through which 80 per cent of the material will pass. Expressions for the work index are given in the original papers 8,9) for various types of materials and various forms of size reduction equipment. 

Combining Bond s work index [Eq. (27)] with Bond s law [Eq. (26)]... 

Measurements of arterial pressure, cardiac output, stroke work index, and pulmonary capillary wedge pressure are particularly useful in patients with acute myocardial infarction and acute heart failure. Such patients can be usefully characterized on the basis of three hemodynamic measurements arterial pressure, left ventricular filling pressure, and cardiac index. One such classification and therapies that have proved most effective are set forth in Table 13-4. When filling pressure is greater than 15 mm Hg and stroke work index is less than 20 g-m/m2, the mortality rate is high. Intermediate levels of these two variables imply a much better prognosis. 

Material Work Index w, Material Work Index w,... 

Bond work index -particle size reduction [SIZE REDUCTION] (Vol 22)... 

The Bond working index W, is the most common description for comminution tasks, and is measured routinely in small-scale laboratory mills ... 

Myocardial oxygen consumption (MVO2) is calculated as pressure-work-index according to Rooke and Feigl (1982). 

Employ an empirical formula that yields the work index directly. The formula [3] is... 

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