Ball Mill Drive
Motor, Gearbox & Gearless Mill Drive Selection
Mill drives are unforgiving: full-load starting torque, continuous 24-hour duty, and a load that changes as the charge and liner wear. The choice between a gearbox, an open girth gear set and a gearless mill drive has to be made on power, speed and maintenance strategy, not on habit.
Send us the mill dimensions, charge and material data. We calculate the absorbed power, select the drive concept, and quote the matched package including the inching drive and lubrication.
What we need from you to select this drive
The more of this you send, the faster and more accurate the selection. If you only have part of it, send what you have — we will tell you what is still missing.
Duty data and site conditions
| Mill dimensions | Internal diameter and length in m, whether single or two-compartment |
|---|---|
| Mill speed | Operating speed in rpm and as a percentage of critical speed |
| Charge | Ball charge in t, filling degree in %, liner type and condition |
| Material | Bond work index in kWh/t, feed size, product fineness, throughput in tph |
| Power supply | Medium-voltage level in kV, frequency, short-circuit capacity, permitted voltage drop |
| Drive concept preference | Gearbox, open girth gear, or gearless mill drive — we will advise if undecided |
| Inching and maintenance | Inching or barring drive required, creep speed, liner handling |
| Site conditions | Ambient temperature, altitude, dust loading, indoor or outdoor |
How we select it
- 1
Calculate the absorbed mill power from dimensions, charge and Bond work index.
- 2
Confirm the starting torque requirement — a mill must start with the full charge lifted, typically 110–130% of rated torque.
- 3
Select the drive concept: gearbox, open girth gear set, or gearless mill drive, against power, speed and maintenance strategy.
- 4
Rate the medium-voltage motor and starter, and check the voltage drop on start against the network capacity.
- 5
Add the inching drive, lubrication unit and condition monitoring, then quote the package.
Selection points that decide the outcome
Starting torque dominates
A mill starting with its charge lifted needs far more than rated torque. Under-rating the starter or motor here is the most common cause of a mill that will not start.
Gearbox versus girth gear versus GMD
Gearbox suits smaller mills, open girth gear is proven to the largest sizes, and a gearless mill drive removes the mechanical transmission but changes maintenance and spares strategy. The right answer depends on your site, not on a catalogue.
Girth gear alignment
Open gear sets depend on correct tooth contact. Specify the alignment procedure and the lubrication system together.
Inching drive is not optional
Liner changes and inspections need a creep drive. Confirm its speed, torque and how it engages.
Twin-drive load sharing
Two pinions on one girth gear must share torque. Specify load sharing and verify it during commissioning.
An indicative package
An example of how a selection comes together. Your figures will differ — this is to show the level of detail we return with a quotation, not a fixed configuration.
Duty
Cement ball mill Ø 3.2 × 13 m · approx. 2,500 kW · 6 kV · two-compartment · continuous duty
Package
- Motor: medium-voltage squirrel-cage motor, 6 kV, rated for full-charge starting torque
- Transmission: Flender open girth gear unit or bevel-helical mill gearbox, rated above the peak starting torque
- Starting: medium-voltage soft starter or VSD depending on the network short-circuit capacity
- Inching drive: auxiliary drive with clutch for liner handling
- Lubrication: forced lubrication and spray system for the girth gear
What we supply for this duty
Medium-voltage motors
- Innomotics SIMOTICS medium-voltage motors
- Innomotics HV series
- ABB medium-voltage motors
- WEG M line and S line medium-voltage motors
Mill gearboxes and girth gears
- Flender mill drive gearboxes
- Flender open girth gear units
- Gearless mill drive solutions on request
Medium-voltage drives and starters
- Innomotics Perfect Harmony GH180, 2.3 – 11 kV / 0.12 – 25 MW
- ABB ACS580MV, ACS6080 and ACS8080
- Soft starters for full-charge starting
Couplings and inching drives
- Flender ARPEX and RUPEX couplings
- Inching and barring drives
- Clutches
Control and monitoring
- Siemens SIMATIC S7-1500 and ET 200
- Vibration, temperature and lubrication monitoring
- B&R X20 for auxiliary control
Ratings we can supply
Typical ratings available
| Motor power | Up to multi-megawatt medium-voltage ratings; state your requirement |
|---|---|
| Medium-voltage drive | Innomotics Perfect Harmony GH180: 2.3 – 11 kV, 0.12 – 25 MW |
| Gearbox torque | Flender mill gearboxes and girth gear units to the largest mill sizes |
| Mill speed | Typically 14 – 20 rpm for ball mills; gearless drives allow variable speed |
| Starting torque | Selected for full-charge starting, commonly 110 – 130% of rated torque |
Brands we supply
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Related applications
Other Brands Available on Request
Beyond the brands shown here, we also source and supply spare units and parts for most international and Chinese industrial brands. Not sure what you have? Send us a photo of the nameplate — we will identify the unit and quote the original part.
Why work with us
- We select the whole drive train — motor, gear unit, coupling, starter and brake — as one matched package.
- You send the duty data; we return the ratings, service factors and alternatives in writing.
- We supply Siemens, Innomotics, Flender, ABB, WEG and B&R, so selection follows your duty, not one catalogue.
- Spare parts and replacements for the same units are available afterwards.
Service & support
Remote and on-site support available, from installation supervision to commissioning and troubleshooting.
What we need from you to quote
For replacements, send a nameplate photo — we identify the exact unit and quote the original part.
- Duty data — power, torque, speed, flow or head, and duty cycle
- Supply voltage, frequency and starting method
- Preferred brand, and your required delivery window
- Quantity, destination port and required delivery date
Answers before you ask
Frequently asked questions
Should I choose a gearbox, an open girth gear, or a gearless mill drive?
It depends on the mill power, speed and your maintenance strategy rather than on a fixed rule. Send us the mill data and we will compare the concepts against your site and quote the one that fits.
Can you supply a mill drive that starts under full charge?
Yes. We select the motor, starter or drive and the transmission for full-charge starting torque, and state the starting torque and the network voltage drop in the quotation.
Do you only supply the eight brands shown on your homepage?
No. We source and supply spare units and parts for most international and Chinese industrial brands, not only the eight brands shown on this site.
I do not know the exact model number. Can you still quote?
Yes. Send us a photo of the nameplate and we will identify the exact unit before preparing the quotation for the original part.
Do you supply genuine original manufacturer parts?
Yes. We supply genuine original manufacturer parts. Send us a photo of the nameplate and we can identify the exact unit before quoting, so you do not need to look up a model number.
Do you provide installation guidance, commissioning and after-sales support?
Yes. We provide installation guidance, commissioning support and after-sales support, remotely or on site depending on your project.
What is the delivery time?
Lead time depends on the product and configuration. We confirm the delivery schedule together with the quotation, so you have a firm date before you order.
Which export documents and certificates can you provide?
We can provide applicable CE and ISO documentation, certificates of origin, packing lists and test reports according to the requirements of your destination country.
What payment terms and incoterms do you work with?
We accept T/T and L/C payment, and quote FOB, CIF or EXW terms to suit your project.
Send the duty data and we will select the package
We return a selection with the ratings, service factors and alternates stated — so you can compare before you buy.
Request a Quotation