critical speed of sag mill

Low SAG Mill Critical Speed

A well implemented SAG control philosophy should be able to vary the mill speed, in response to variations in feed characteristics. If the feed ore becomes softer, then the mill control system should respond to reduce the mill speed. You may not need to keep adding grinding media either, if the issue persists too long.

Modelling SAG milling power and specific energy

N/Nc is the fraction of the SAG mill critical speed. Scw is the solid concentration by weight fraction in the SAG mill feed. 3.2. Power model. As can be seen in Fig. 4, the effect of the independent variable (% −6 +1″) on the mill power consumption is similar for all mills analysed, but the position of the trend lines is different for each one.

SAG Mill Grinding Circuit Design

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Optimizing your SAG mill operation

WEBA further explanation is required to explain the importance of designing the SAG mill chamber to draw required power at optimum operating conditions of 75% …

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 e ect when the mill is under the condition of 80% critical speed and 15% fill …

Autogenous and Semi-Autogenous Mills

The mill speed is 70% of the critical speed. 9.4. A high aspect SAG mill had an ID of 6.0 m and the length measured 4.0 m along the central line. The mill was charged with ore having an S.G. of 2.65 and the load was 40% of the mill volume. The grinding media steel balls occupied 12.2% of the mill volume.

(PDF) 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 ...

SAGDesign Test

The crushed ore is then ground in a SAGDesign SAG mill (489 mm inside diameter x 163 mm EGL), seen here, that operates with parameters similar to commercial SAG mills (26% total charge; 11% steel load, 15% ore load; and rotation at 76% of critical speed). The SAGDesign SAG mill with the lid on in the loading position.

(PDF) Toward a Simple Approach Determining Single Stage SAG mill …

F is the mill speed expressed as a percentage of critical speed . f(Ar) is a function of mill aspect ratio (this function is not published) ... type of SAG mill popular in North America and for ...

Operation Analysis of a SAG Mill under Different …

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 increase again; the optimal steel ball ratio in the SAG mill depends on the simulation time (mill actual working time) and the limitation of the rated power.

Mill Speed

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.

Keys to best practice comminution

The Pilot SAG mill had a fixed speed drive and ran at 75% of critical speed. ... Operating a SAG mill at a fixed 75% critical speed corresponds to the operational strategy adhered to in the 1960′s and 1970′s. 11. Little has been said about the impact of under-sizing a SAG mill, on the operators who are trying to operate it, and on ...

Ball Mill Critical Speed

A Ball Mill Critical Speed (actually ball, rod, AG or SAG) is the speed at which the centrifugal forces equal gravitational forces …

Milling curves as a tool for characterising SAG mill performance

SAG mill performance curves for the South Deep mill running at 60, 70 & 75% critical speed …

Process optimisation for your SAG Mill

SAGwise will reduce the number of critical impacts inside your SAG Mill, protecting your liners from critical impacts while lifting performance. ... Mill speed; Mill water; Downloads. Fact sheet and brochures. Advanced process control for …

Energies | Free Full-Text | Operation Analysis of a SAG Mill …

In the simulation, to study the effect of mill speed ratio and mill fill level ratio on the fracture effect of the SAG mill, as shown in Figure 6a,b, when the mill speed ratio is between 65% and 90% of the critical speed, the total mass curve of the rock below 25 mm in the mill presents normal distribution. When the speed is 80% of the critical ...

Research on performance of a laboratory-scale SAG mill …

In this paper, the working process of the SAG mill is taken as the research object, and the mill fraction of critical speed, lifter face angle, and rock shape are taken as the influence factors. Through the DEM-EMBD coupling method, the effects of the influencing factors on the torque and the electromechanical characteristics of the SAG …

SAG mill performance curves for the South Deep mill …

Download scientific diagram | SAG mill performance curves for the South Deep mill running at 60, 70 & 75% critical speed from publication: Milling curves as a tool for characterising SAG mill ...

Design of the 40 foot SAG Mill Installed at the Cadia …

The design of the 40 foot diameter SAG mill motor was such that up to a mill operating speed of 74% critical, power would be delivered at constant torque. Above 74% and up to the maximum of 85% of critical speed, constant power would be delivered. The following Figure 2 demonstrates the effect as well as the vendor design estimates.

Research on performance of a laboratory-scale SAG …

When the SAG mill is in the stable running stage, the average value of the motor load torque increases first and then decreases, and it is the maximum when the …

What is critical speed of a SAG mill?

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 ...

Advanced Simulation for Semi-Autogenous Mill …

Due to the size of SAG mills, pilot plants are usually used for research purposes to improve the control strategies. In cases where a pilot-scale is not available for test, simulations us ing ... grinding media flow rate and the mill critical speed. The model output variables are: power-draw, load level, ball load, mineral discharge rate

SAG Mill Process Control

In my experience, SAG Mills are normally variable speed, and Ball Mills are normally fixed speed. There are multiple ways to provide variable speed, the common ones are WRIM+LRS+SER or SCIM+VSD, the top of the range is gearless mill drives. Victor Bergman. 8 years ago.

AG

Product Size: All passing 6 mesh with 80% passing 20 mesh. Net power from pilot plant: 16.5 KWH/ST. Mill, gear and pinion friction multiplier: 1.025. Mill Power required at pinionshaft = (240 x 16.5 x …

A CRITICAL REVIEW OF GRINDING DESIGN …

index by using values from an operating circuit. Its value is only valid at the stated SAG product size. • Transfer size (T80) is the term used to describe the SAG mill product that is sent to the ball mill. For peak performance and balancing the power available in the SAG mill and ball mill, the transfer size must be measured and controlled.

(PDF) Design of the 40 foot diameter SAG mill …

Dunne et al. (2001) state the initial design of the Cadia Gearless Mill Drive called for 20 MW at a 9.02 RPM rated speed. The tent diagram assuming volumetric loadings of 13% balls and 25% total ...

Optimisation of the Cadia Hill SAG mill circuit

operating mill speed of 74% of critical. SAG mill availability was . expected to be 94%, giving an annual processing rate of 17Mtpa of . monzonite ore. As the deposit contains around 9 percent of ...

Recent advances in dem modelling of tumbling mills☆

Only part of the mill can be modelled in this way and axial transport cannot be examined. Full SAG mill with approximate PSD Our first sag mill example is of a 10 m diameter and 4 m long SAG mill with flat end walls. It has 72 lifters with face angles of 5 degrees. The fill level is 30% (by volume) and the mill rotates at 75% of critical speed.

Materials | Free Full-Text | Optimization of the SAG …

Silva et al. fit a power equation and an energy equation specific to the design of SAG mills, using them to predict energy consumption as a function of mill size, internal load level and density, …

Choosing a SAG Mill To Achieve Design Performance

A 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 volume load. Recent studies in the three-foot diameter SAG mill are instructive. The following graph shows the relevant facts as Figure 2.

SAG Mill | Autogenous and Semi-Autogenous Mills

Single stage SAG Mills are very beneficial in reducing CAPEX for plants with a staged throughput approach. When future tonnage is to be increased, the SAG Mill can feed downstream ball milling to boost capacity. Fuller-Traylor SAG/AG Mills range in size from 4.3m through 12.2m in diameter with powers as high as 28,000 kW.