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Mill Power

What your drive should be pulling, worked out from the charge you measured. Then compare it with what the ammeter actually reads. If the two disagree, one of them is wrong — and that is the most useful thing this tool does, because neither the tape measurement nor the ammeter can tell you that on its own.

Why this matters now

Clinker reduction, high electricity prices and tighter cement specifications put the grinding circuit under pressure. The fastest gains usually come from finding the real constraint before changing equipment or operation.

What this tool helps decide

Turn charge, speed and geometry into specific energy and compare it with the ammeter before changing operation, media or equipment.

What subscription adds

Build a connected grinding audit: save every mill separately, reload previous measurements, compare changes over time and issue an editable report for the plant team.

Connected to the industry conversation around clinker-factor reduction, grinding energy, blended cement and quality control reported in World Cement, CemNet and Global Cement.See process-tool plans

Your mill and your drive

Shared with your other tools. Diameter, chamber lengths, tape readings, ball weights and mill speed are remembered in this browser, so the volume loading tool and this one always describe the same mill. Change it here and it changes there.

The mill

Mill inside diameter Inside the lining, in metres.

Mill speed Revolutions per minute of the shell.

First chamber

LengthMetres, inside the lining.

Distance down to the balls Millimetres, from the lining at the top to the top of the balls.

Weight of the balls Tonnes per cubic metre, as they sit. Around 4.5 for big balls.

Second chamber

LengthMetres, inside the lining.

Distance down to the ballsMillimetres.

Weight of the balls Tonnes per cubic metre. Around 4.65 for small balls.

The drive

Motor efficiency Per cent. Large mill motors are typically 94 to 96.

Gearbox efficiency Per cent. Girth gear and reducer together, typically 94 to 96.

What the ammeter actually reads Kilowatts at the motor. Leave 0 if you do not have it — the comparison then stays blank instead of guessing.

Production

Cement leaving the mill Tonnes per hour, for the energy per tonne figure.

HOW THE MILL TURNS

WHAT THE DRIVE MUST DELIVER

Critical speed

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Mill speed, % of critical

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C1 how full

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C2 how full

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C1 balls

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C2 balls

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C1 lever the drive lifts

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Torque factor (approx)

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C1 grinding power

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C2 grinding power

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Grinding power total

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Drive should pull

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Energy per tonne

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Ammeter reads

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Difference

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Total charge

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What this means

Where the charge figure comes from

This power is only as good as the charge behind it. If the ammeter disagrees, re-measure the free height before you touch anything else.

Re-check the charge

How the numbers are worked out

The lever. A turning mill lifts its charge up one side. How far the weight sits from the centre line is the lever the motor works against — workbook formula #1. It depends only on the diameter and how far down the balls start.

The power. Pn = 0.514 × tonnes × u × rpm × diameter × lever, workbook formula #2, once per chamber. That is the power going into grinding.

At the motor. Divide by motor and gearbox efficiency — formula #3 — and you get what the ammeter should show. That is the only number you can actually go and check.

One approximation, and it is on the board. The torque factor is 1.36 − 1.2 × filling/100, described in your own mill-formulas.js as a Duda-style approximation. It is the single fitted number here; everything else is geometry or a workbook formula. It has its own cell so you can watch what it does.