Categories: Brytning

Worm Gearbox for Belt Conveyor Systems

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 snäckväxel 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.

Branschapplikationer och användningsfall

In a typical belt conveyor drive arrangement, the snäckväxel sits between the electric motor and the conveyor head drum. Key application points include:

Head-end drive units on horizontal conveyors — steady torque, self-lock on stop
Inclined conveyor drives — self-locking prevents roll-back under loaded belt weight
Take-up winch drives — precise low-speed tension control on counterweight systems
Belt weigh feeder drives — accurate, vibration-free low-speed output

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.

Tekniska specifikationer och urvalsguide

Använd tabellen nedan för att identifiera lämplig modell. Viktiga parametrar inkluderar utväxling, utgående vridmoment, axeldimensioner och husmaterial. Använd alltid rätt Servicefaktor (SF) för din arbetscykel.

Parameter	Typiskt intervall/värde	Urvalsanteckningar
Förhållande	5:1 – 100:1 (single-stage)	Two-stage tandem available up to 3,600:1
Utgående vridmoment	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
Höljets material	Aluminium alloy / Ductile iron GGG40	Stainless steel 316 available on request
Mounting Type	Foot / Flange / Shaft-mounted	All standard orientations F1–F8
Skyddsklass	IP65 standard; IP66 / IP69K optional	Specify at order for outdoor / washdown duty

► Servicefaktor (SF): Uniform load SF=1.0 | Moderate shock SF=1.25–1.5 | Heavy shock / 24 h continuous SF=1.75–2.0

► Omgivningstemperatur: Standard units rated –10°C to +40°C. Australian high-ambient sites (>45°C) require high-temperature lubricant and 15% thermal derating.

NMRV/NRV-seriens snäckväxel

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.

Efterlevnad och kvalitetsstandarder

✓ ISO 9001:2015
Certifierat kvalitetsledningssystem. Varje enhet tillverkas och inspekteras enligt ett dokumenterat kvalitetsledningssystem med fullständig spårbarhet.

✓ CE Certification
CE-märkt enligt EU:s maskindirektiv. Brett accepterad i australiska och nyzeeländska ingenjörsprojekt.

✓ IEC 60034 motorgränssnitt
IEC-standardfläns- och axeldimensioner. Direktmonterad kompatibilitet med alla större motormärken.

✓ IP65 / IP66 Protection
Dammtät och högtrycksvattenbeständig. Standarden för utomhusinstallationer i Australien.

Fallstudier

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Case Study 1 — Open-Cut Coal Mine, Hunter Valley NSW

Brytning
Inclined Belt Conveyor

Kundens smärtpunkt: 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.

Lösning: 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.

Resultat: 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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Case Study 2 — Mineral Processing Plant, Western Australia

Brytning
Horizontal Ore Conveyor

Kundens smärtpunkt: 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.

Lösning: NRV series worm gearbox (ratio 40:1, 1,800 N·m) with upgraded FKM double-lip seals and synthetic PAO gear oil.

Resultat: 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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Case Study 3 — Grain Handling Terminal, Port of Geraldton WA

Bulk Handling
Belt Weigh Feeder

Kundens smärtpunkt: A grain terminal’s weigh feeder was overspeeding by up to 8%, causing inaccurate throughput measurement and regulatory compliance issues.

Lösning: NMRV-063 worm gearboxes (ratio 80:1) replaced the helical-bevel units. Smooth, low-backlash output eliminated speed hunting corrupting the load cell signal.

Resultat: 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

Varför välja oss?

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20+ års tillverkning
ISO-certifierad produktion sedan 2003. Snäckväxlar levereras till fler än 60 länder.

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Teknisk fjärrsupport
Videosamtaldiagnostik över australiska tidszoner. Snabb respons utan besök på plats.

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OEM/ODM-anpassning
Icke-standardiserade axlar, ihåligt hål, specialanpassade flänsar och utväxlingar. Fullständig ritning tillgänglig.

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Fabriksdirektvärde
Ingen distributörsmarginal. Transparent volymprissättning med betydande besparingar på återkommande beställningar.

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Lager och snabb leverans
Standard NMRV/NRV-ramar finns i lager. Brådskande beställningar hanteras för expressfrakt.

Vanliga frågor

▼ What is the difference between NMRV and NRV worm gearboxes for conveyor applications?

NMRV units feature an aluminium alloy housing — lighter and suited to lighter-duty or indoor drives. NRV units use cast iron — greater rigidity and thermal mass, preferred for continuous heavy-load mining conveyors. Both share identical internal geometry and are interchangeable in mounting footprint within the same frame size.

▼ How do I calculate the required reduction ratio for my belt conveyor?

Required ratio = Motor RPM ÷ Required drum RPM. Drum RPM = (Belt speed m/s × 60) ÷ (π × drum diameter m). For example, 1.5 m/s belt on a 400 mm drum needs 71.6 RPM. With a 1,400 RPM motor, required ratio is 19.6:1 — select 20:1 or 25:1. Contact our engineering team for a free calculation.

▼ Does a worm gearbox on an inclined conveyor require a separate anti-rollback device?

For inclinations up to approximately 20° and loads within the rated self-locking torque, worm geometry alone provides sufficient anti-rollback protection. Above 20° inclination or for very high-inertia belt loads, a supplementary backstop or brake is recommended as safety redundancy.

▼ What IP protection rating should I specify for a mine-site belt conveyor gearbox?

IP65 is the minimum for all open mine-site conveyor applications. For conveyors near water sprays, dewatering areas, or underground wet zones, specify IP66 or IP67. Our standard NMRV/NRV range is IP65 as standard, with IP66 and IP67 available as factory options.

▼ What lubricant is recommended for worm gearboxes on mining conveyors in hot Australian climates?

Standard mineral ISO VG 220–460 is suitable for ambient temperatures up to 35°C. For outback sites regularly exceeding 40°C, synthetic PAO ISO VG 320 is recommended — it reduces internal operating temperature by 8–12°C and extends the oil change interval from 2,000 hours to 5,000+ hours.

▼ Can worm gearboxes be used for reversing conveyor applications?

Yes — worm gearboxes can be driven in both directions at the same rated torque. The self-locking feature applies in both directions. For applications requiring free coasting in reverse, a low-lead-angle (non-self-locking) ratio must be specifically selected. Consult our technical team to confirm self-locking status for your chosen ratio.