Worm Gearbox for Slurry Agitator / Mixer

Worm Gearbox for Slurry Agitator & Mixer — Robust Drive for Abrasive Process Fluids

Slurry agitators in mineral leaching tanks, flotation conditioning vessels, and tailings storage facilities impose demanding requirements on their drive systems: continuous operation, chemically aggressive process fluids, and the ever-present risk of impeller submergence in dense abrasive slurry. Our cast-iron worm gear reducers with heavy-duty tapered roller bearings and reinforced sealing are built specifically for this service. See the full application scope on our applications page.

Operating Principles & Design Considerations

A slurry agitator drive must handle not only the continuous fluid-drag torque from the impeller, but also start-up torque spikes (up to 3× running torque) when the impeller is restarted in settled slurry. The worm gear drive’s large reduction ratio in a single stage generates the high output torque needed from a compact, standard motor input. Internal heavy-duty conical roller bearings absorb the combined radial and axial forces transmitted from the agitator shaft through the impeller’s hydraulic reaction forces.

Material Specifications

Housing: Grey or nodular cast iron with anti-corrosion epoxy coating — absorbs vibration from hydraulic pulsing and impeller imbalance.
Worm Wheel: Tin-bronze ZCuSn10Pb1 — high load capacity and excellent thermal conductivity to manage heat generated under sustained agitation duty.
Bearings: Heavy-duty tapered roller bearings (replacing standard deep-groove ball bearings) — handles the combined overhung load from the long agitator shaft and impeller mass.
Shaft Sealing: Mechanical face seal or multi-lip seal with purge port — prevents slurry ingress along the output shaft.

Technical Parameters

Parameter	Specification
Gear Ratio	10:1 – 80:1
Output Torque	Up to 8,000 Nm (standard)
Overhung Load Capacity	Enhanced by heavy-duty tapered roller bearings
Housing Material	Cast iron GG25/GGG50; epoxy-coated
Output Shaft Options	Solid; hollow bore (torque arm); extended shaft
Bearing Type	Tapered roller (standard for agitator duty)
Protection Rating	IP55–IP66 depending on installation
Service Factor	1.75–2.5 (continuous agitation with density variation)
Duty	S1 continuous — designed for 24/7 operation

Overhung Load (OHL) Calculation: Agitator shafts impose significant radial (bending) loads on the gearbox output shaft due to impeller hydraulic forces and shaft weight. Always provide impeller diameter, shaft length, and process fluid density when requesting a gearbox selection — standard catalogue radial load ratings may be exceeded for long agitator shafts without a bottom stabiliser bearing.

Compliance & Standards

Slurry agitator worm gear drives comply with ISO 9001:2015 quality management and carry CE certification. Input flanges meet IEC 60072 B5/B14 motor standards. For ATEX/IECEx Zone 1 or Zone 2 classified leaching and flotation circuits, EX-rated motor adapters with certified flameproof interfaces are available. IP ratings from IP55 to IP66 are standard; mechanical face-seal options for submersible agitators are available on request.

Application Case Studies

Nickel Laterite Leach Plant — NT — High-acid leach tank agitator

Challenge: Sulphuric acid vapour corroded standard housing paint within 3 months; oil contamination followed.

Solution: Specified two-pack epoxy-coated housing, 316SS output shaft stub, and purge-type mechanical face seal.

Result: No corrosion or oil contamination in 30 months; maintenance reduced to annual seal inspection.

Bauxite Processing — Gladstone, QLD — Conditioning tank slurry agitator

Challenge: Tapered roller bearing failure every 6 months due to excessive overhung load from 2.4-metre impeller shaft.

Solution: Upgraded to heavy-duty tapered bearing housings with additional external shaft support bearing; resized to 60:1 ratio.

Result: Bearing MTBF extended from 6 months to over 36 months; downtime cost reduced by $120k/year.

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Coal Slurry Tank — Hunter Valley, NSW — Dense medium cyclone feed agitator

Challenge: Frequent speed variations in coal feed rate caused motor hunting and gear tooth wear.

Solution: Fitted VFD-compatible worm gearbox (input speed 300–1,500 rpm); synthetic gear oil for wide thermal range.

Result: Motor current stabilised; gear tooth wear eliminated; plant throughput consistency improved 12%.

Our Competitive Advantages

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Tapered Roller Upgrade

Heavy-duty tapered roller bearings standard on all agitator-duty models — not an expensive add-on.

Chemical Compatibility

Housing coatings and shaft materials matched to your specific leach chemistry — acid, alkali, or oxidant.

Custom Shaft Extensions

Extended output shafts and hollow-shaft configurations machined to your agitator assembly dimensions.

24/7 Duty Rating

All agitator models rated S1 continuous — no thermal derating for prolonged operation.

Remote Commissioning

Online commissioning support via video call for remote mine sites — reduces travel costs for start-up assistance.

Frequently Asked Questions

▼ How do I specify the service factor for a slurry agitator gearbox?

Slurry agitators with dense, variable-density process fluid should use a service factor of 2.0–2.5. If the agitator starts under settled slurry (e.g., after an overnight shutdown), apply an additional start-up torque allowance of 2–3× running torque. The gearbox peak-torque rating must not be exceeded under any foreseeable operating condition.

▼ What is overhung load and why does it matter for agitator gearboxes?

Overhung load (OHL) is the radial force applied to the output shaft by the weight of the impeller assembly and hydraulic reaction forces during agitation. Excessive OHL causes premature bearing failure and output shaft fatigue fracture. Always calculate OHL from impeller mass, shaft length, and process fluid drag and provide this data when selecting an agitator gearbox.

▼ Can I use a standard conveyor worm gearbox for a slurry agitator?

Not recommended. Standard conveyor gearboxes use deep-groove ball bearings optimised for axial load, not the radial overhung loads of agitator service. Agitator-duty gearboxes incorporate tapered roller bearings with higher radial load capacity. Using an incorrectly specified bearing type leads to premature failure within months in agitator service.

▼ What sealing solution prevents slurry from entering the gearbox via the output shaft?

For standard splash/vapour environments, multi-lip shaft seals with a purge port (grease-purged labyrinth) are adequate. For applications where the output shaft is submerged or subject to direct slurry spray, a mechanical face seal (cartridge type) should be specified. Mechanical face seals provide positive positive-pressure isolation between the process fluid and the gear oil.

▼ How does VFD (variable frequency drive) control affect worm gearbox performance?

VFD control is fully compatible with worm gearboxes. At reduced frequencies (below ~30 Hz), the internal cooling fan of the motor provides less airflow — the motor must be derated or a separate forced-cooling blower fitted. The gearbox itself is unaffected by VFD output waveform. Use synthetic gear oil when running at very low input speeds (<300 rpm) to ensure adequate lubrication of the worm mesh.