16 10 2014 Study of the grinding balls distribution inside the mill

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Thu, 16 October 2014, 18:39:05 UTC

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Study of the grinding balls distribution inside the mill

2 Analysis of the samples

All we need:

- A balance

Procedure: - The balls are assembled visually by sizes - The biggest balls (from 100mm or more to 50mm) are weighed one by one - For the lower dimensions, we will assemble the balls of the same size by lots in order to save time - The balls from 50mm to 30mm are assembled by lots of 5. After, each lot of five balls is weighed. In the calculation list which will follow, each ball of one lot will have the average weight of the lot (total weight of the lot divided by 5) - The balls from 30mm to 15mm are assembled by lots of 10. After, each lot of ten balls is weighed. In the calculation list which will follow, each ball of one lot will have the average weight of the lot (total weight of the lot divided by 10) - The media lower than 15mm are often scraps and will be weighed together. A good approximation of the number of small pieces is enough - It is also interesting to count the balls which have a defect. This can be achieved with balls having a diameter greater than 40mm. - One can see some pictures of the lots by size here below:

Example: - In this example, only one sample in the middle of the mill has been taken - Total weight of the sample: 567,9 kg - Number of balls: 480 - Here below, the raw list of this sample with the weight of the balls and the balls with defect in red

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16 10 2014 Study of the grinding balls distribution inside the mill

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- After the weighing, we must classify the balls by category. For this, we convert the weight in diameter and we have the following categories (with specific gravity of 7,8kg/dm3):

- And we have the following results:

- Important notice: In this sample, there were not balls under 40mm and no scraps. The reason was that this mill was always working full of material. The pulp was going out by the door at mill outlet. Normally, a charge at the equilibrium must have a gradation from the top-up size (here 80mm) up to 10mm (when the ball becomes a chip and leaves the mill).

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