Screw conveyor

01

Size diameter and speed from the capacity table

KWS Manufacturing's screw conveyor engineering guide gives the selection steps: calculate the required capacity in ft³/h, take the recommended trough loading for the material from its bulk material table, choose the diameter whose capacity at maximum rpm exceeds the requirement at that loading, and divide the required capacity by the capacity at 1 rpm to get the speed. [1]

Its capacity table for 30A loading lists, for example, 9 in at 5.5 ft³/h per rpm (maximum 100 rpm, 545 ft³/h), 12 in at 12.9 (90 rpm, 1,161 ft³/h), 16 in at 31.2 (80 rpm, 2,496 ft³/h) and 24 in at 109.0 (65 rpm, 7,085 ft³/h). At 15% loading the same 16 in screw is limited to 45 rpm and 702 ft³/h; at 45% it reaches 130 rpm and 6,071 ft³/h. [1] KWS notes that the maximum speeds were developed for non-abrasive, free-flowing materials, that it recommends lower speeds than those maximums for industrial applications, and that the table applies to control-fed conveyors, not flood-loaded screw feeders. [1]

Its types page says conveyors are designed at 15, 30 or 45% trough loading: 45% for light, free-flowing, non-abrasive materials and 15 or 30% for denser, sluggish or more abrasive materials. [2]

Editorial calculation: 16 in is about 406 mm, and 31.2 ft³/h per rpm is about 0.88 m³/h per rpm, so the 2,496 ft³/h maximum at 80 rpm is about 70.7 m³/h (1 ft³ = 0.0283 m³). [1]

Give the supplier the material name, bulk density, particle and lump size, moisture, temperature, abrasiveness and flow behaviour, required capacity in t/h or m³/h, length and incline, inlet and outlet positions, feeding device, sealing and dust requirements, materials of construction, motor voltage and enclosure, and the site's hazardous-area classification.

02

Adjust for pitch, flights, incline and power

KWS gives capacity factors that raise the selection capacity when pitch is reduced or flights are modified: 1.00 for standard pitch, 1.50 for 2/3 pitch, 2.00 for 1/2 pitch and 0.67 for 1½-diameter long pitch; cut flights 1.92, 1.57 and 1.43 at 15, 30 and 45% loading; and cut-and-folded flights 3.75 at 30% and 2.54 at 45%. [1]

Its worked example conveys 10 t/h of unslaked lime at 60 lb/ft³ (333 ft³/h) at 30A loading, using 2/3-pitch, cut-and-folded flights to mix in transit: the selection capacity is 1.50 × 3.75 × 333 = 1,873 ft³/h, a 16 in screw is selected, and the speed is 1,873 ÷ 31.2 = 60 rpm. [1]

On inclines KWS says efficiency losses are minimal up to 10°, are 10–40% between 10° and 20°, and that above 45° the conveyor is treated as a vertical screw conveyor; it recommends the lowest possible incline. [2] It defines total shaft horsepower as friction horsepower plus material horsepower divided by drive efficiency, taking 0.88 for a shaft-mount reducer and motor, and says material horsepower below 5 HP should be corrected for potential overload. [3]

Material characteristics change the design: KWS lists non-sparking construction, pressure-tight troughs, shaft seals and inert-gas purging for flammable or explosive materials, sealed troughs for very dusty materials, lower loading and speed for materials that soften or aerate, and ribbon or shaftless flights for sticky materials. [4]

Editorial calculation: the example's 333 ft³/h is about 9.4 m³/h; written in metric, the request would be 10 t/h at about 960 kg/m³, mixed in transit, over about 4.6 m (15 ft).

03

Compare what suppliers offer

Suppliers linked to this page list screw conveyors; each card links to the page reviewed.

The listings reviewed range from drilling-cuttings conveyors for solids-control systems to tubular stainless and shaftless conveyors for powders, slag and process plants; ask each for capacity at your material's loading, speed, power and materials of construction.

04

Trace what each part controls

This is a functional reference built from the sources cited; it is not one maker's specification.

05

Fill the specification fields with values for your material

A screw conveyor quotation needs values for your material and layout. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

06

Send the material, capacity and layout data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Material: [name; bulk density; lump size; moisture; temperature]
Behaviour: [abrasive; sticky; dusty; aerates; flammable]
Capacity: [t/h or m³/h]
Layout: [length; incline; inlet; outlet]
Feed: [feeding device upstream]
Construction: [trough or tube; materials; seals]
Drive: [voltage; enclosure; location]
Site: [hazardous area; cleaning]

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