Mixer & Agitator Drive
Gearbox, Motor & Seal Selection
Mixer duty is defined by viscosity: the same impeller in a thin liquid and in a viscous one differ by an order of magnitude in absorbed power. The gearbox also carries the full shaft bending moment, which is often what really sets the rating.
Send us the vessel geometry, medium and duty. We select the gearbox, motor, drive and seal arrangement, and quote them as one package with the shaft load rating stated.
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
| Vessel | Tank volume in m³, diameter and liquid height, baffled or unbaffled |
|---|---|
| Medium | Viscosity in cP at operating temperature, density, solids content, corrosiveness |
| Impeller | Impeller type, diameter in mm, number of impellers, tip speed |
| Speed | Operating speed in rpm, and whether variable speed is required |
| Shaft | Shaft length, diameter, steady bearing, whether dry running can occur |
| Sealing | Mechanical seal or stuffing box, seal flush plan, dry running tolerance |
| Power supply | Voltage, frequency, phases, hazardous area classification |
| Duty | Continuous or batch, cycle time, cleaning regime |
How we select it
- 1
Establish the impeller power number and calculate the absorbed power at the operating viscosity.
- 2
Select the gearbox on torque and on the shaft bending moment and axial load, not on power alone.
- 3
Check the critical speed of the shaft assembly against the operating speed range.
- 4
Select the motor, drive and starting method for the required turndown.
- 5
Specify the sealing arrangement and quote the package with the shaft load rating stated.
Selection points that decide the outcome
Viscosity dominates the power
Absorbed power scales sharply with viscosity. State the viscosity at the operating temperature, and at the worst case if the process thickens.
Shaft load, not just torque
Mixer gearboxes carry the full overhung shaft load. Selecting on motor power alone is the usual cause of premature bearing failure.
Critical speed of a long shaft
Long mixer shafts have a first critical speed that must sit outside the operating range. Confirm it during selection, especially with variable speed.
Seal selection and dry running
Seal face materials and the flush plan follow from the medium and the pressure. Confirm whether the seal can tolerate dry running.
Hazardous area classification
Solvents and fine powders carry ignition risk. State the zone classification so the motor, gearbox and seal are specified correctly.
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
Tank 50 m³ · medium 2,000 cP · two hydrofoil impellers · 60 rpm · continuous · ATEX zone 2
Package
- Gearbox: Flender mixer gearbox selected on torque and shaft bending moment, with the bearing arrangement rated for the overhung load
- Motor: ~30 kW, IE3 or IE4, IP55, specified for the hazardous area classification
- Drive: VSD for turndown, with the critical speed checked across the range
- Sealing: Sulzer mechanical seal with the correct flush plan for the medium
- Optional: KSB or Sulzer agitator supplied complete where the whole unit is preferred
What we supply for this duty
Mixer gearboxes
- Flender mixer gearboxes with shaft load carrying bearings
- Flender helical and bevel-helical gear units
- Flender geared motors
Agitators and mixers
- KSB agitators and mixers
- Sulzer mixers and agitators
- Sulzer static mixers for in-line mixing
Motors
- Innomotics SIMOTICS low-voltage motors
- WEG W22 and W21
- ABB IEC motors, IE5 SynRM
- Flameproof designs for hazardous areas
Seals and drives
- Sulzer mechanical seals and seal support systems
- Siemens SINAMICS G120X and G120C
- ABB ACS380, ACS480 and ACS580
Control
- Siemens SIMATIC S7-1200 / S7-1500
- B&R X20 system
- Torque, temperature and level integration
Ratings we can supply
Typical ratings available
| Motor power | Commonly 0.75 – 250 kW for mixer duty; higher on request |
|---|---|
| Output speed | Typically 10 – 300 rpm, matched to the impeller |
| Selection basis | Torque plus shaft bending moment and axial load, not power alone |
| Sealing | Sulzer mechanical seals with the flush plan specified for the medium |
| Hazardous area | Flameproof and increased-safety designs available; state the classification |
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
How is a mixer gearbox selected?
On torque and on the shaft bending moment and axial load together. Selecting on motor power alone ignores the overhung shaft load, which is the usual cause of premature bearing failure.
Do you supply complete agitators as well as the drive?
Yes. We supply KSB and Sulzer agitators and mixers complete, and we also supply Flender mixer gearboxes, motors and drives for existing vessels.
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