Worm Gearbox for Screw Conveyors

Worm Gearbox for Screw Conveyors — Sealed Power for Powder & Bulk Solids Handling

Screw conveyors — also known as auger conveyors or helical screw feeders — are the go-to solution for moving powders, granules, cement, grain, fertiliser, and other bulk solids through enclosed troughs or pipes. The worm gearbox driving the screw shaft must provide two things above all else: high torque at low speed and near-perfect sealing against the very material being conveyed. A single gram of cement or talc entering the gearbox housing accelerates wear dramatically. Our worm gear reducers are configured with flange-direct mounting to the screw trough end-plate, aligning worm output shaft directly with the screw shaft — eliminating any shaft gap where powder can accumulate.

⚙️ Primary Function

Rotate screw helix at 30–120 rpm to propel bulk material axially through a sealed trough. Motor speed (1 400 rpm typical) reduced in a single worm stage — no need for secondary reduction.

Critical Requirement

Flange-direct connection provides full mechanical seal between gearbox and trough — eliminating exposed shaft length where powder would collect, cake, and migrate into bearings.

Screw Conveyor Design & Worm Drive Integration Details

A screw conveyor trough section terminates at a bearing-and-seal end plate. The worm gear drive is bolted directly to this plate via a machined register spigot (IEC B5 flange or custom machined bolt circle). The output shaft of the worm reducer couples to the screw shaft via a key and set-screw, often supplemented by a rigid half-coupling for ease of disassembly.

Key technical considerations unique to screw conveyor duty:

Axial (thrust) loading — the conveyed material exerts a reaction force on the screw helix that transmits as axial load to the output shaft. Our worm gearboxes use taper-roller bearings on the output side to handle combined radial and axial loads without premature bearing fatigue.
Overload at start-up — compacted or bridged material in the trough creates a locked-rotor condition at start. Worm reducers with self-locking geometry (ratio ≥ 30:1) provide built-in break-out torque resistance; specify SF 2.0 for this scenario.
Seal configuration — dual-lip seal + labyrinth groove on the output shaft extension into the trough prevents powder ingress regardless of trough pressure differentials. IP65 rated minimum; IP66 for pressurised pneumatic conveying.
Material contact zone — the shaft stub inside the trough should be stainless steel (AISI 304 or 316) for food, pharmaceutical, or corrosive material applications.

Worm Gearbox Technical Specifications for Screw Conveyors

Parameter	Available Range	Typical Screw Conv. Selection
Gear Ratio	5:1 – 100:1	15:1 – 50:1 (screw 30–90 rpm)
Output Torque	10 – 4 500 N·m	50 – 800 N·m depending on screw diameter
Flange Type	B5 (face flange) / B14 (small flange)	B5 flange preferred for direct trough mounting
Output Shaft Bearing	Deep-groove or Taper-roller	Taper-roller — handles axial thrust load
Shaft Material	45# steel or SS 304	SS 304 for food / pharma duty
Housing	Aluminium alloy / Grey cast iron	Cast iron for continuous operation
IP Rating	IP65 / IP66	IP65 minimum; IP66 for pressurised conveying

Selection by Conveyed Material

Apply an environmental/material correction to the service factor: abrasive materials (cement, silica sand) add +0.5 to SF; sticky materials (wet clay, moist grain) add +0.25; corrosive vapours present — upgrade to IP66 and request epoxy-coated housing. Contact the engineering team with your material bulk density and moisture content for a tailored recommendation.

Quality Certifications & Standards

Our screw conveyor worm gearboxes are produced under strict quality management:

✅ ISO 9001:2015 Certified

✅ CE Marked (2006/42/EC)

✅ IEC B5/B14 Motor Flange

✅ IP65 / IP66 Rated

✅ Material Test Certs (worm wheel bronze)

Five Screw Conveyor Case Studies

#	Industry / Application	Customer Challenge	Solution & Result
1	Cement Plant Fly ash dosing screw	Ash penetrated the reducer housing within 2 months; two seal replacements per quarter.	Flange-mount worm reducer, IP66, labyrinth + V-ring seal stack. Seal interval extended to >18 months.
2	Flour Mill Flour transfer auger	Product contamination concern; existing reducer used non-food-grade oil causing compliance issues.	Stainless steel shaft, H1 food-grade lubricant, IP65 sealed. Passed FDA facility audit without remarks.
3	Fertiliser Plant Granule metering screw	Ammonium nitrate fumes corroding housing; replacement every 6 months.	Epoxy-coated cast iron housing, stainless shaft stub, IP66. First corrosion inspection clear at 30 months.
4	Plastic Extrusion Resin pellet feeder	Static charge on pellets caused intermittent position errors; required electrically grounded drive.	Worm reducer with earthing lug on housing; electrostatic discharge path confirmed with continuity test.
5	Mining Underground coal screw feeder	ATEX zone requirement; no certified gearbox available locally at acceptable price.	ATEX II 2G Ex IIB T4 worm reducer supplied from our OEM partner range; ATEX documentation package included. Passed inspection first attempt.

Why Choose Our Worm Reducers?

Vertically Integrated Manufacturing

We cast the bronze worm wheels, machine the housings, and assemble under one roof — full traceability, zero outsourcing risk.

OEM Flange Engineering

Custom flange bolt circles, register diameters, and keyway positions machined to your trough drawing — no adaptor plates needed.

Global Technical Support

Engineering consultations available by video call across all time zones — share your AutoCAD trough drawing and we’ll design the interface.

Volume Pricing

MOQ from 1 unit for prototype — tiered pricing for 10, 50, 200+ unit orders. Cost-per-unit drops 20–35 % at batch production volumes.

Frequently Asked Questions

What output torque do I need for a 250 mm diameter screw conveyor moving cement at 80 rpm?

For a 250 mm screw handling cement (bulk density ~1 500 kg/m³) at 80 rpm, a rule-of-thumb torque estimate is 180–320 N·m depending on trough fill ratio and material cohesion. Apply SF 1.75 for abrasive cement, giving a required reducer rated torque of 315–560 N·m. We recommend our size 110 or 130 cast-iron worm unit with ratio 17:1 or 20:1. Please provide exact trough length and fill factor for precise sizing.

How is the gearbox mounted to the screw trough end plate?

The preferred method is a B5 face-flange configuration: the gearbox output face (with machined register spigot) bolts directly onto the trough end plate using 4–8 bolts. The output shaft extends through the end plate to the screw shaft coupling. This eliminates any exposed shaft length and provides a rigid, sealed joint. We supply 2D and 3D mounting dimension drawings for all frame sizes.

Is a worm gearbox suitable for reversing screw conveyor operation?

Yes — worm gear drives operate in both rotational directions without modification. For reversing operation, ensure the lubrication system (oil splash) remains effective regardless of rotation direction; our symmetrically located oil fill ports ensure this. Note that self-locking worm stages (ratio ≥ 30:1) will resist back-driving from material weight during reversing — this is usually desirable.

What seal type prevents fine powder from entering the gearbox?

We use a three-stage seal stack on the output shaft: primary double-lip NBR seal, labyrinth groove to create a grease-packed barrier, and a V-ring seal as a final dust wiper. For very fine powders (<50 µm particle size), we additionally recommend a positive-pressure purge connection (1–2 bar compressed air) on the shaft bore to create outward airflow that prevents particle migration.

Can the worm reducer be mounted in any orientation on a screw conveyor?

Standard worm reducers are designed for horizontal mounting (worm shaft horizontal). Vertical or inclined mounting positions require a modified oil fill quantity and may need additional vent/breather relocation. Specify the mounting angle when ordering and we will supply the unit with adjusted oil level marks and appropriate breather positioning.