Belt conveyors are the circulatory system of Australia’s mining and bulk-materials industry, moving millions of tonnes of coal, iron ore, grain, and mineral aggregate every year. Behind every reliably running conveyor is a precisely selected drive unit — and the worm gearbox has earned its dominant position through a combination of self-locking geometry, compact right-angle output, and robust high-torque delivery.
The self-locking characteristic is particularly critical on inclined conveyors: when power is removed, the irreversible worm geometry prevents the loaded belt from reversing under gravity. This eliminates the need for a separate backstop or motorised brake on many installations, simplifying the mechanical design and reducing maintenance exposure.
Standard NMRV and NRV series aluminium or ductile-iron worm gearboxes are available in frames from 025 to 150, providing output torques from 2.6 N·m up to 4,200 N·m and reduction ratios from 5:1 to 100:1 in a single compact stage. Two-stage tandem configurations extend this to 3,600:1.
In a typical belt conveyor drive arrangement, the worm gearbox sits between the electric motor and the conveyor head drum. Key application points include:
Materials: Worm shaft in surface-hardened alloy steel 20CrMnTi (HRC 58–62). Worm wheel in centrifugally cast phosphor bronze. Housing in ductile iron GGG40 with IP65 dust-and-jet-water sealing.
Working principle: The helical worm thread engages the bronze wheel teeth at 90°. Back-driving from the wheel side is geometrically prevented when the lead angle is below the friction angle — this is the self-locking mechanism at the heart of safe conveyor operation.
Use the table below to identify the appropriate model. Key parameters include reduction ratio, output torque, shaft dimensions, and housing material. Always apply the correct Service Factor (SF) for your duty cycle.
| Parameter | Typical Range / Value | Selection Notes |
|---|---|---|
| Ratio | 5:1 – 100:1 (single-stage) | Two-stage tandem available up to 3,600:1 |
| Output Torque | 2.6 – 4,200 N·m | Dependent on frame size 025–150 |
| Input Shaft Diameter | 11 – 42 mm | IEC 60034 standard flange sizes B5/B14 |
| Output Shaft Diameter | 14 – 50 mm (solid) | Hollow bore available from frame 030 up |
| Housing Material | Aluminium alloy / Ductile iron GGG40 | Stainless steel 316 available on request |
| Mounting Type | Foot / Flange / Shaft-mounted | All standard orientations F1–F8 |
| Protection Class | IP65 standard; IP66 / IP69K optional | Specify at order for outdoor / washdown duty |
► Service Factor (SF): Uniform load SF=1.0 | Moderate shock SF=1.25–1.5 | Heavy shock / 24 h continuous SF=1.75–2.0
► Ambient temperature: Standard units rated –10°C to +40°C. Australian high-ambient sites (>45°C) require high-temperature lubricant and 15% thermal derating.
NMRV / NRV Series Worm Gearbox
Available in frame sizes 025 through 150. Single-stage reduction ratios 5:1 to 100:1. Output torque up to 4,200 N·m. Aluminium or ductile iron housing. IEC B5/B14 motor flange. IP65 standard, IP66/IP67 optional. Synthetic or mineral oil lubrication.
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Customer Pain Point: A coal mine was experiencing rollback on a 15° inclined conveyor each time the belt tripped under overload. The mechanical backstop failed twice in six months, causing 18 hours of downtime per incident.
Solution: NMRV-110 worm gearboxes (ratio 60:1, ductile iron, IP65) were installed on both drive stations. The inherent self-locking eliminated the need for the external backstop entirely.
Result: Zero rollback incidents over 14 months. Annual maintenance cost reduced by 35%. The mine standardised the same model across three further inclined conveyors on site.
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Customer Pain Point: A WA iron ore processor needed to replace an ageing helical gearbox generating 74 dB(A) of gear noise, with oil changes every 1,500 hours due to worn lip seals.
Solution: NRV series worm gearbox (ratio 40:1, 1,800 N·m) with upgraded FKM double-lip seals and synthetic PAO gear oil.
Result: Operating noise reduced to 61 dB(A). Oil change interval extended to 5,000 hours. Zero seal leaks during two 12-month inspection cycles.
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Customer Pain Point: A grain terminal’s weigh feeder was overspeeding by up to 8%, causing inaccurate throughput measurement and regulatory compliance issues.
Solution: NMRV-063 worm gearboxes (ratio 80:1) replaced the helical-bevel units. Smooth, low-backlash output eliminated speed hunting corrupting the load cell signal.
Result: Throughput accuracy improved to within 0.3% of certified scale. Port authority compliance reinstated within one week.
NMRV / NRV series worm gearboxes — frame sizes 025 to 150, manufactured to ISO 9001:2015
20+ Years Manufacturing
ISO-certified production since 2003. Worm gearboxes shipped to 60+ countries.
Remote Technical Support
Video-call diagnostics across Australian time zones. Rapid response without on-site visits.
OEM / ODM Customisation
Non-standard shafts, hollow bore, custom flanges and ratios. Full drawing review available.
Factory-Direct Value
No distributor margin. Transparent volume pricing with significant savings on repeat orders.
Stock & Fast Dispatch
Standard NMRV/NRV frames in warehouse stock. Urgent orders processed for express freight.
Our engineers are ready to recommend the right worm gearbox model, ratio, shaft configuration, and mounting arrangement for your application.
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