# How to Optimise the Speed of the Ball Mill

• Date Submitted: 12/06/2012 11:03 PM
• Flesch-Kincaid Score: 76.1
• Words: 258
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The speed of a Ball Mill is in measured in revolutions per minute (rpm) of its drum.To measure this, you need a stopwatch (preferably that rings!) and a thick felt pen. Mark a bold line lengthwise on the outside of the drum. Then start the loaded ball mill and allow it to reach its steady loaded speed. Then press the stopwatch timed for a minute, and count the number of times the bold line comes into view before the stopwatch rings.
The speed of rotation (rpm) of the loaded ball mill is critical to success:too slow, and the milling takes too long; while too fast, and the contents (balls, ore and water) slam against the wall, inhibiting milling.Now use trial-and-error to discover the critical speed at which the centrifugal force pins the balls against the inside of the drum - they cease to roll and no longer fall. For this, the ball mill should be fitted with a variable speed drive.
The critical speed can also be derived by 42.3/D0.5 where D is the diameter in METRES. For instance, a 90cm diameter ball mill has a critical speed of 44 rpm. For efficient milling, the critical speed is too high - you need now to determine the optimal speed which is about 70-75% of the critical speed. For instance a 90cm diameter ball mill with a critical speed of 44 rpm has an optimal speed of 31 to 33 rpm. Get beneficiation,Mineral Processing,ball mill From http://www.ballmill8.com