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Get PriceA further explanation is required to explain the importance of designing the SAG mill chamber to draw required power at optimum operating conditions of 75 critical speed and less than 30 by
A Ball Mill Critical Speed actually ball rod AG or SAG is the speed at which the centrifugal forces equal gravitational forces at the mill shell’s inside surface and no balls will fall from its position onto the shell The imagery below helps explain what goes on inside a mill as speed varies Use our online formula The mill speed is typically defined as the percent of the Theoretical
According to available literature the operating speeds of AG mills are much higher than conventional tumbling mills and are in the range of 80–85 of the critical speed SAG mills of comparable size but containing say 10 ball charge in addition to the rocks normally operate between 70 and 75 of the critical speed
Presently SAG mills are mainly driven with variable speed drives Due to the high torque required by the mill low speed motors are generally synchronous machines The mill is a low dynamic system offer a wide field weakening range The low speed solution motor used with the drive has a nominal frequency varying from 10 – 20Hz
The speed of milling is the distance in FPM Feet per minute in which the circumference of the cutter passes over the work The spindle RPM necessary to give a desired peripheral speed depends on the size of the milling cutter The best speed is being determined by the kind of material being cut and the size and type of the cutter used width and depth of cut finished required type of
Oleg D Neikov in Handbook of NonFerrous Metal Powders 2009 Tumbling Ball Mills Tumbling ball mills or ball mills are most widely used in both wet and dry systems in batch and continuous operations and on a small and large scale Grinding elements in ball mills travel at different velocities Therefore collision force direction and kinetic energy between two or more elements vary
Mill load sharing – Maintains equal torques on dual pinion mills throughout the whole speed range Controlled rollback – Prevents backlash and reduces downtime Mill power ride through – Keeps the mill operating even under voltage dips Overduty cycle – Avoids unexpected downtime if the mill
MW It has been the industry standard for SAG mills above 13 MW capacity However pinion systems to 8 MW per pinion and dual motor systems with quadruple pinions extend the range of gear driven mills to a theoretical limit of 32 MW The Ernest Henry SAG mill 11 MW is currently the largest twin pinion single drive mill installed in Australia
Figure 18 Approx two months mill speed histograms in a South American copper concentrator It can be unmistakably observed that for this SAG mill during these two months the variable speed feature on the SAG mill is used the mill speed is varied between around 7 and 10 rpm This is not surprisingly as it concerns a SAG mill
In most cases the ideal mill speed will have the media tumbling from the top of the pile the shoulder to the bottom the toe with many impacts along the way The ideal mill speed is usually somewhere between 55 to 75 of critical speed Critical Mill Speed Critical Speed left is the speed at which the outer layer of media centrifuges
The speed of milling is the distance in FPM Feet per minute in which the circumference of the cutter passes over the work The spindle RPM necessary to give a desired peripheral speed depends on the size of the milling cutter The best speed is being determined by the kind of material being cut and the size and type of the cutter used width and depth of cut finished required type of
Updates on geared vs gearless drive solutions for grinding World’s largest geared drive 2x8500kW Wushan China operating Among the many reasons that geared drives on large SAG mills are not favoured is due to not having an efficient variable speed drive option 60 to 80 critical speed which is required for process reasons
predicted the required SAG mill specific energy and were likely to not reach design throughput limitations in SAG mill speed due to severe breakage of mill liners at higher speeds 6 P a g e and highly competent ore with DWI values in the range of 82 99 kWhm3 equivalent to
Figure 18 Approx two months mill speed histograms in a South American copper concentrator It can be unmistakably observed that for this SAG mill during these two months the variable speed feature on the SAG mill is used the mill speed is varied between around 7 and 10 rpm This is not surprisingly as it concerns a SAG mill
Variable Speed Single or double pinion driving systems Designed to drive and control the speed of the medium voltage motors coupled to the SAGAG ball and HPGR mills with single or double pinion the MVW01 frequency drive uses state of the art technology through a multilevel structure with medium voltage IGBTs reducing the harmonic currents on the motor to extremely low levels
The critical speed of rotation is the speed in rpm at which an infinitely small particle will cling to the inside of the liners of the mill for a complete revolution 1 CS 43305 √Mill Diameter where CS is the theoretical critical speed of rotation and is the mill speed rpm Mill diameter is the nominal inside diameter of the mill m
singlestage SAG mills to the largest mill in the world – with a 40foot diameter and 28 MW of motor power Ball mills Ball milling is the most common application for horizontal tumbling mills Outotec offers a full range of ball mills to suit a wide variety of duties from a few hundred kW all the way up to 20 MW and beyond Rod mills
Figure 83 Simplified calculation of the torque required to turn a mill RI FULWLFDO VSHHG 3RZHU Figure 84 The effect of mill speed on the power drawn by a rotating mill The liner profile and the stickiness of the pulp in the mill can have a significant effect on the actual critical velocity Mills usually operate in the range 65 82 of
Dec 12 2016 · If P is less than 80 passing 70 microns power consumption will be Ball Mill Power Calculation Example A wet grinding ball mill in closed circuit is to
Optimising the capacity of your SAG mill is crucial to avoiding downtime and liner wear and damage With variances in mill ore feed rate mill speed and slurry density critical impacts can occur in your SAG mill The speed at which these variances are adjusted for is thus crucial for minimizing damage and optimizing liner life
Delivering unmatched SAG Mill speed and power Sub and hyper synchronous mill motor speed control is offered without speed deadband The SER delivers 100 per cent of rated nameplate motor shaft power at above synchronous speeds an exclusive benefit of this SER technology
Dec 12 2016 · If P is less than 80 passing 70 microns power consumption will be Ball Mill Power Calculation Example A wet grinding ball mill in closed circuit is to
Figure 83 Simplified calculation of the torque required to turn a mill RI FULWLFDO VSHHG 3RZHU Figure 84 The effect of mill speed on the power drawn by a rotating mill The liner profile and the stickiness of the pulp in the mill can have a significant effect on the actual critical velocity Mills usually operate in the range 65 82 of
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