sag mill critical speed

Design of the 40 foot SAG Mill Installed at the Cadia Gold ...

Speed (fr. Critical) Grate aperture SAG mill base power was estimated from pilot plant data at 7.8 kWh/t, the basis was a SABC circuit of 8% ball charge. Maximum SAG mill power was determined by deducting the installed ball mill pinion power of 7.95

SAG Mill Optimization using Model Predictive Control

Control of -SemiAutogenous Grinding(SAG) mill weight is an example of an important process that exhibits many of these aspects. Maintaining the SAG mill weight at the optimum value is critical for achieving maximum grind rate efficiency and mill production (Powell, M.S., van der Westhuizen, A.P., & Mainza, A.N. 2009).

Evolution of SAG Mill Process Control at the Xstrata ...

revealed a thermal limitation in the 3000hp LCI variable speed drive system at low mill speeds. This event resulted in variable speed operation being suspended, and the mill being operated at a fixed speed (76% of critical) until a thorough analysis of the event could be completed. DEVELOPMENT OF A SAG MILL CONTROLLER

What is derivation of critical speed? - Answers

The critical speed of a SAG mill is the speed in RPM's at which centrifugal force causes the material being ground to be held against the inside of the shell. This speed is only dependent on the ...

Mill drives: the desire for increased power and the ...

the output speed of any mill drive system, whereas that of a GMD refers to actual motor speed in rpm or mill speed in% of critical speed, (% C.S.), depending upon the extent of shell liner/lifter wear. The charts in Figure 2 (after Barratt and Brodie, 2001) illustrate the following lines in examples for a 24 MW Base

Paper # 25 - Copper Mountain Overview on the Grinding ...

Table 2 - general SAG mill circuit and ore data Specification Data Operating circuit Closed-circuit Operating mill ball charge 15 percent by volume Operating mill total charge 32 percent by volume Mill speed 10.08 RPM (76 percent of critical speed average) Ore specific gravity (sg) 2.77 Ore bulk density 1.64 tonnes/m3 Table 3 - SAG mill ...

Operation Analysis of a SAG Mill under Different ...

Simulation results under the ∅ 5250 × 500 mm mill model show that the mill operates with the optimal effect when the mill is under the condition of 80% critical speed and 15% fill level; the power of the mill does not increase linearly with an increase in the mill speed ratio, but will decrease after 85% of the critical speed, and finally ...

FREDA REBECCA SAGMILLING CIRCUIT OPTIMIZATION

the SAG mill amounting to 51.2 t/h affecting mill capacity as this took space and limited the capacity for new feed. Using ModSim simulator, incorporation of a 100 micron screen on the cyclone ... balls usually below 10% and running at a fraction of …

(PDF) Influence of feed size on AG / SAG mill performance

Build-up in critical size: It is well established from the earliest use of AG and SAG mills that the build-up of competent critical size material, can drop throughput to half (Morrell and Valery ...

SAG PARTICLE PHYSICS - ffden-2.phys.uaf.edu

1. A mill speed approaching 80% of critical can optimize grinding action and reduce wear. A charge with a increased trajectory does less work and more damage as grinding balls are flung against the opposite side of the shell instead of falling down on top of the central mass. 2.

SAGMILLING .:. Mill Critical Speed Determination

The "Critical Speed" for a grinding mill is defined as the rotational speed where centrifugal forces equal gravitational forces at the mill shell's inside surface. This is the rotational speed where balls will not fall away from the mill's shell. Result #1: This mill would need to spin at RPM to be at critical speed.

Semi Autogenous Grinding Mill - an overview ...

In a SAG mill the dimensions of the mill were 9.75. m × 3.5 m and the specific gravities of the mineral and that of the balls charged were 4.1 and 7.9 respectively.. The mill was rotated at 75% of its critical speed when 8 % of the mill volume was charged with grinding balls.Estimate:1. The mill power drawn, 2. The maximum mill filling possible.

Grinding Mill Computer Model

• Second SAG Milling Conference - Barratt MILLCALCv2a 6 19/02/2004. Standard Mill Programmes Metallurgical Energy Requirement - Autogenous Mill/SAG Mills Pc - Power for crushing 10 11 ... Mill Critical speed Crit Crit D = 42.3 n - …

What is critical speed of a SAG mill? - Answers

AG/SAG mills as a primary grinding stage in a circuit with or without additional stages of comminution; ... Many of these mills operate at higher mill speeds (nominally 90% of critical speed) and often use "grid" liners to form an autogenous liner surface. These mills typically grind ROM ore in a single stage.

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SAG MILL M/C Condition. Critical . Machine Condition Report. Machine Technical Data's. ISO 10816 Classification Class-IV <7.1-Normal, 7.1 to 18.0-Marginal, >18.0- Critical Motor Speed. 660 RPM approximately Gear box Input Speed 660 RPM approximately Gear box output Speed 133 RPM approximately Mill Speed 8 RPM approximately Foundation:-

Increase throughput and capacity in SAG mills

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.

formula for calculating the critical speed of a ball mill

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

Kecepatan Ccritical Grinding Mill

Ball Mill Kecepatan Kritis. Formula Kecepatan Kritis Ball Mill apa kecepatan kritis ball mill formula untuk kecepatan kritis ball mill mill grinding jan a ball mill critical speed actually ball rod ag or sag is the speed at which the formula derivation ends up as follow critical speed is nc nbsp ball milling a ball mill is a type of grinder used to grind and blend materials for use in mineral

Ball Mill Critical Speed - Mineral Processing & Metallurgy

Ball and SAG Mills are driven in practice at a speed corresponding to 60-81% of the critical speed, the choice of speed being influenced by economical considerations. Within that range the power is nearly proportional to the speed. Mill …

Automated SAG Mill Speed Control Using On-contact ...

adjust mill speed. • New rules for the expert system speed control: High LDL signal and low bearing pressure, reduce speed and prevent "metal on metal" operation. • Two vibration systems installed and in operation at Gold Corp Peñasquito on their two 2265 TPH SAG mils.

What's the Difference Between SAG Mill and Ball Mill ...

The biggest characteristic of the sag mill is that the crushing ratio is large. The particle size of the materials to be ground is 300 ~ 400mm, sometimes even larger, and the minimum particle size of the materials to be discharged can reach 0.1 mm. The calculation shows that the crushing ratio can reach 3000 ~ 4000, while the ball mill's ...

EX-4.AP - SEC.gov

The mill is estimated to be capable of drawing the 5500 kW at the pinion at 75% of critical speed with a 12 to 15% or greater ball charge and a total charge of 28%. The mill should be able to operate at the design conditions (10% ball charge, 28% total charge) in the speed range of 50% to 75% of critical speed over the full wear life of the liners.

'SER' – Slip Energy Recovery Grinding Mill Speed Control

With our SAG mill running at 65.4% critical speed (mill @ 8.7 RPM), the SER motor speed reference is 850 RPM or 85% of 1000 RPM. We are recovering approximately 1.2 MW of slip energy; the power ...

White paper, September 2015 SmartMill™: Exceed your ...

mills. SAG mills of over 40-foot diameter have been constructed. Like the ball mill, the AG/SAG mill will have a critical rotation speed above which grinding ceases. Mill motor types There are three common motor types that drive the grinding mills described above: – Gearless motors. These variable-speed motors range up to 30 MW and have the ...

ONLINE SAG MILL PULSE MEASUREMENT AND …

minutes at 60%, 70% and 80% critical speed. The data was collected on a continuous basis and force spectrum and the force histogram were generated for each run. The histogram shown here paves the way for SAG mill signature. In other words, a SAG mill would exhibit a specific force histogram under a set of operating conditions.

Mill Speed - Critical Speed - Paul O. Abbe

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 against the wall. Second Critical Speed (middle) is the speed at which the second layer of media centrifuges inside the first layer.

formula for critical speed of a ball mill

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 …

Automated SAG Mill Speed Control Using On-contact ...

Therefore the SAG mill speed could not be controlled using the microphone based signal and instead was manually controlled/set by the control room operator. Thus operation/speed of the mill could and would change significantly based on a particular operator running the mill and their overall level of mill operation experience and skill.

Ball mill - Wikipedia

A ball mill, a type of grinder, is a cylindrical device used in grinding (or mixing) materials like ores, chemicals, ceramic raw materials and paints.Ball mills rotate around a horizontal axis, partially filled with the material to be ground plus the grinding medium. Different materials are used as media, including ceramic balls, flint pebbles, and stainless steel balls.

Benchmarking: Bond - Copper Mountain - SAGMILLING

Raising the SAG speed to 78% of critical speed (10.4 RPM) has little effect due to the drop-off in power observed in a Loveday model using Barratt's published Power Numbers above 76% of critical speed. The model predicts a negative phantom cyclone effect. This is an odd result, but does match one observation on a hard ore (Boddington circuit ...