Sample report (example case, illustrative values)

Case

Mill and ore

Charge size distribution (by mass, at the start of the run)

Media Ore · each class is one size, drawn as a straight step between its diameter and the next.

Key findings

• Mill power draw averaged 1,105 kW (standard deviation 34 kW, 3.1 %) over 8 revolutions, 23.6 to 65.0 s.
• 11 % of the power goes into the mill liner and 89 % is dissipated within the charge.
• Impact forces account for 49 % of the power and shear (sliding) forces for 51 %.
• Specific power is 17.9 kW per tonne of charge.
• The mill runs at 75 % of critical speed.
• The charge sits against the shell from a toe angle of about -48° to a shoulder angle of about 120° (from the bottom of the mill, positive in the direction the shell moves), averaged over 3 snapshots.
• Over the latest revolution, the highest simulated liner cell pressure (9.65e+08 Pa) is 3x the average across the liner (3.48e+08 Pa): impacts are concentrated at a few contact points rather than spread evenly.
• The highest simulated liner pressure this revolution is at -8°, 41° from the charge's toe angle (-48°), so the worst wear point is not simply where the charge lands.
• Liner wear extrapolates to 0.9 mm per day (real life).

Power draw

The shaded window is used for the average. It starts one revolution after the mill starts turning.

Torque-arm power, a second measure: the weight of the mill contents (61.56 t) times the horizontal offset of their centre of gravity from the axis, times the mill speed, over 10 frames of the last revolution: 1143.0 kW, 1.03 of the DEM power. The DEM power is the energy the contacts dissipate; the torque arm is the work to hold the charge lifted, as in the published mill power models.

Power split

Latest values from HeartBeat.txt, cumulative over the energy averaging window of the run.

Throughput

Mill power

Slurry in the mill: 117.0 t, slurry filling the voids of the tumbling charge (voidage 0.53); grinding media and ore of the DEM charge 281.3 t.

The DEM charge is dry. The slurry fills 100 % of the charge voids at 1.83 t/m3 and adds mass. The slurry also takes friction and damping out of the charge, 5.5 % of the power in a plant ball mill survey (the draw running and after grind-out). The no-load power is Morrell's equation for a gear and pinion drive at 75 % of critical speed.

Discharge size distribution

No plant throughput was given, the throughput is the baseline estimate. Enter a measured plant throughput in the Throughput window (Mill Configuration, Throughput button) to get a throughput factor for this mill.

Ore in the DEM charge

Grate discharge

The SPH run has the real grate, fed by a thin slice of the mill, starts with the discharge chambers filled and runs for about two revolutions. The first revolution flushes the filled chambers; the capacity is the mean slurry discharge over the complete revolutions after it (counted from the start of the discharge), times the slurry density and the pulp solids, reduced by the blinded share of the open area.

Fines: the ore finer than the DEM ore keeps the energy of the finest DEM ore and also takes the ball-ball collision power, 607 kW (607 kW with the energy scale), shared by mass and by Austin's size dependence (alpha 1, Lambda 2.5), peaking at the feed size each ball is sized for by Bond's ball size equation (133 mm balls 42 mm, 102 mm balls 25 mm).

Ore: A 75 %, b 0.5, t-family alpha 0.8, grate 25 mm; energy scale 1 and breakage cycle 40 s are baseline constants of the model; the grate classifies the discharge as in the JK SAG model, ore below 1 mm leaving with the water; the discharge rate is solved from the throughput (40 1/h). Energy window 17.72 to 64.96 s. The baseline was set on two plant SAG mills and a plant ball mill survey, see the user guide.

Charge motion

Mid-plane slice viewed along the mill axis at the start of the motion and at the end of each revolution. Colours use the same range in every image. Click an image to enlarge.

Motion start

frame 122, t = 6.10 s (-0.02 s from the revolution end) · toe -75°, shoulder 75°

Revolution 1

frame 240, t = 12.00 s (-0.02 s from the revolution end) · toe -35°, shoulder 145°

Revolution 2

frame 359, t = 17.95 s (+0.02 s from the revolution end) · toe -35°, shoulder 140°

Charge shape

Toe and shoulder are the ends of the arc where the charge touches the shell, found from the particles within 1.5 largest diameters of the shell in the mid-plane slice. A stable charge gives flat lines.

Liner wear and pressure

The pressure and force values reset every revolution (WorldTriangleForcePeak's ResetFreq), so they show the latest completed revolution's own peak and average, not a running worst-case since the start of the run: a single explicit-integration step spike early in a long run no longer inflates these numbers for every revolution after it. Total liner wear and wear rate are still a running total, since a meaningful wear rate needs the whole run. Wear shown as real life (run speed-up 1 x, wear window 0.000683 days).

Liner wear against scans

Real liner scans of a full-scale SAG mill (not the example case above), shown to illustrate the wear workflow: dots are the measured crest height lost along the mill axis at 64, 90 and 102 days, solid lines are the learned wear law fitted to the scans, and the dashed line is its forecast for 120 days.

Liner parts

Per revolution of steady motion, 8.0 revolutions from 17.72 to 64.96 s. Impact energy is the normal energy the particles dissipate on the liner; wear is the Archard wear depth in real life (um per revolution of the mill, the run speed-up divided out), use it to compare cases rather than as a liner life. Wear shown as real life (run speed-up 1 x, wear window 0.000683 days).

Where the plate is hit between the bars

Plate values across one pitch of the lifters (638 mm), averaged over the 48 pitches. Shaded bands are the bars.