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Tetrahedrons and Spherical Balls Compared: An interested operator furnished 1,000 pounds of tetrahedrons for comparison with spherical balls. The tetrahedrons were all about the same size and the average weight of each was the same as for a 1 3/8- inch spherical ball. Four pairs of tests with tetrahedrons and round balls, respectively, are shown in table 22. The loads weighed

A stock of 300 pounds of 1 5/8-inch sillimanite balls was donated by the Champion Spark Plug Co. for grinding tests. They were true spheres, white, and all about the same size. Although native sillimanite has a density of 3.2, the artificial product had a density of only 2.56, this being the lowest density included throughout all the experiments. Another

Selection of Volume of Ball Loads in Continuous Dry Open Circuit Grinding: The tests reported in tables 19 and 20 were made in cooperation with a large cement-manufacturing company that wished to obtain more grinding for the power expended. The ball load in its clinker- grinding mills was 18 percent of the mill volume and the company did not deem it

Table of ContentsCritical Speed & Power Speed CurvesEffect of Particle Size and Mill Power The study of grinding is a study of cause and effect. The pre-ponderance of the literature is on the latter—effect. It seems that the study began at the end, with effect, and worked backward without going back far enough to reach the cause. The cause is

In table 3 of a recent publication a report was made on the use of pipes (instead of rods) stuffed with different materials to give grinding media of different densities when the dimensions were always the same. The mill had a large discharge opening. There it was shown that through a range of densities from 2.89 to 7.30 and a

Table of ContentsBatch Mill Grinding of OreOpen Circuit Grinding Batch Mill Grinding of Ore Batch grinding affords the best opportunity for first studies of pulp consistency. Table 6 shows some of the results. The consistencies ranged from 80 to 20 percent solids. The initial five tests will be considered first and the last one will be mentioned later. In the last test

Table of ContentsEffect of Rod Mills Ore Charges & SpeedsEffect of Rods Sizes & Speeds  In a study of rod-mill discharge openings of different sizes, four pairs of tests were made at speeds of 40, 50, 60, and 70 percent of critical. In each pair the discharge openings were 8.0 and 4.5 inches, respectively. The tests were conducted so that

Table of ContentsSelective and Non-Selective GrindingLarge Balls & Small Rods Compared When the mill is rotated without feed or with very fine feed, the rods are in parallel alignment and in contact with one another for their full length. New feed entering at one end of the mill causes the rod charge to spread at that end. This produces a

Table of ContentsBatch Ball Mill GrindingWet and Dry Open Circuit Ball MillingType of Grind with Different Amounts of Ore Charges in Wet and Dry Ball Milling Batch Ball Mill Grinding Capacities and efficiencies in wet and dry ball milling at different speeds and ore charges have been discussed in the foregoing pages. The results are summarized in table 16, which

Table of ContentsDry-Batch Ball Milling with Various Ore ChargesDry-Batch Ball Milling with Equal Ore Charges and at Various Speeds Chert, which is very hard, and dolomite, which is moderately hard, were selected for use in a study of the effect of different speeds and ore charges in batch tests. Mill, ball load, and pulp consistency always were the same. Results

When the amount of ore in the mills was the same, no appreciable difference between batch and continuous open-circuit ball-mill grinding was found. This should be so, because the progression in particle size for the duration of a batch run would be expected to be the same as the progression from the feed to the discharge ends in a continuous