GUIDEVERSUS / CONVEYING
Belt, pipe, screw, airslide or bucket elevator? Conveyor types compared
How the main mechanical conveyor types for bulk materials compare — belt, pipe, screw, airslide and bucket elevator — on material, capacity, distance, incline, containment, energy and maintenance, and how to pick between them.
Every conveyor type is the right answer to some duty and the wrong answer to most others. The comparisons below are the ones we run in the first hour of a study: what the material allows, what the route demands, and only then what each option costs to buy, run and maintain. Pneumatic conveying is deliberately left out — it is a different family with its own trade-offs — as are vibrating and drag conveyors, which have narrower niches.
Which conveyor type suits which material and route?
| Type | Best for | Avoid when | Capacity | Distance | Incline |
|---|---|---|---|---|---|
| Belt | Almost any lumpy, granular or fibrous material; high tonnage | Very fine dry dusts without enclosure; steep lifts | Very low to very high | Metres to kilometres | Limited by material (commonly ~15–20°); more with chevron/cleated belts |
| Pipe conveyor | Dusty, spillage-sensitive or environmentally exposed routes; curved paths | Very large lumps; short simple runs where a belt is cheaper | Low to high | Hundreds of metres to kilometres | Steeper than open belt (commonly up to ~30°) |
| Screw | Short runs, metering, sticky, hot or hazardous materials in an enclosure | Very abrasive or large-lump material; long distances | Low to medium | Metres to tens of metres | Any, with reduced capacity as angle rises |
| Airslide | Fine, dry, fluidisable powders (cement, fly ash, alumina, raw meal) | Anything that will not fluidise: moist, coarse, fibrous | Medium to high | Tens of metres per section | Downhill only, on a slight slope |
| Bucket elevator | Vertical lift of powders, granules and small lumps, including hot | Sticky material that will not discharge; very large lumps | Low to high | Vertical, tens of metres | Vertical |
Belt conveyor
- Where it wins
- The lowest energy per tonne carried, the broadest material range and the longest reach. Nothing else moves hundreds of tonnes an hour over a kilometre as cheaply.
- Where it struggles
- Fine dry powders escape as dust unless the belt is enclosed; inclines are limited by what the material will hold on a smooth cover; every transfer point is a dust and spillage source in its own right.
- What the design turns on
- Belt width and speed against bulk density, lump size and surcharge angle; idler selection (troughing angle and spacing); the transfers (transfer point design); tracking and cleaning.
- Maintenance profile
- Idlers, cleaners, skirt seals and the belt itself. Predictable, and mostly done from the walkway.
Pipe conveyor
- Where it wins
- A belt that rolls itself into a tube after loading: the material is enclosed for the whole run, the route can curve horizontally and vertically, and the return strand can carry material too. Ideal where dust, weather or spillage matter and where a straight line is impossible.
- Where it struggles
- Higher capital cost and drive power than an open belt of the same capacity; larger lumps limited by the pipe diameter; curve radii need space; the belt needs care to keep the overlap closed.
- What the design turns on
- Pipe diameter against lump size and fill, curve radii, idler panel design, transition lengths at loading and discharge. The pipe conveyor note sets out when the closed belt earns its cost.
- Maintenance profile
- More idlers per metre than an open belt, but no spillage clean-up and fewer transfer points because curves replace them.
Screw conveyor
- Where it wins
- Simplicity in an enclosure: one rotating part, no belt, no cleaners. Good for metering out of a hopper, for hot or hazardous material, and for short links between machines. Variable-pitch screws are excellent feeders.
- Where it struggles
- Abrasive material wears the flight and trough quickly; fibrous or sticky material wraps and builds up; capacity falls sharply with incline; hanger bearings in long screws are a wear and blockage point.
- What the design turns on
- Diameter, pitch and speed against trough loading (a fraction of the cross-section, lower for difficult materials), and the details for the material — see screw conveyors for sticky and fibrous materials.
- Maintenance profile
- Flight and trough wear; hanger bearings; seals at the shaft ends. Inspection requires opening the trough.
Airslide (air-gravity conveyor)
- Where it wins
- A closed trough with a porous membrane: low-pressure air fluidises a fine powder so that it flows downhill on a slight slope like a liquid. No moving parts along the run, very low power, fully enclosed, quiet.
- Where it struggles
- It only works for materials that fluidise and stay fluidised — dry, fine, air-retentive powders. Moisture, coarse fractions or fibres stop it. It cannot go uphill, and the slope consumes height that has to be recovered by an elevator somewhere.
- What the design turns on
- Slope, width, air volume and pressure, membrane choice, and above all whether the material fluidises — see how airslides work and when they don't.
- Maintenance profile
- Membrane condition and air quality (dry, oil-free). Otherwise the lowest of any type here.
Bucket elevator
- Where it wins
- The only economical way to lift material vertically in a small footprint. Belt or chain, centrifugal or continuous discharge, it covers powders to small lumps and can take hot material with the right components.
- Where it struggles
- Sticky material that will not leave the bucket; large lumps; anything that must not be degraded by the discharge. Also the most sensitive of the five to poor feeding — an under-filled or over-filled boot wears buckets and belt fast.
- What the design turns on
- Discharge type against material — see centrifugal vs continuous discharge — then belt or chain, bucket type and spacing, speed, boot feeding and head geometry.
- Maintenance profile
- Buckets, belt or chain tension and wear, head and boot pulleys or sprockets, bearing temperature and speed monitoring. Access is vertical, so it needs planning.
How do the types compare on cost, energy and upkeep?
| Belt | Pipe | Screw | Airslide | Bucket elevator | |
|---|---|---|---|---|---|
| Capital cost per metre | Low–medium | Medium–high | Low | Low | Medium (per metre of lift) |
| Energy per tonne | Lowest | Low–medium | Medium–high | Very low | Medium |
| Containment | Open unless covered | Closed | Closed | Closed | Closed |
| Material degradation | Low | Low | Medium | Very low | Depends on discharge type |
| Sensitivity to material change | Low | Medium | High | Very high | Medium |
| Maintenance access | Along the run | Along the run | Trough opening | Minimal | Vertical — plan it |
Combining types: the usual plant pattern
Real plants rarely use one type. A typical powder route is a belt or truck reception, a bucket elevator into a silo, an airslide out of it to a bagging or loading point, and a screw feeder at each metering step. A typical lumpy-material route is belts throughout with a shuttle conveyor to distribute across bays, and one elevator where the level has to be recovered. The skill is in the interfaces — each change of type is a transfer with all the dust and spillage questions that come with it — and in not forcing a type past its comfort zone because it is already on site.
The Flow Finder on this site filters the equipment we engineer and supply by task, material and industry; every type discussed here is on it. For a duty that does not fit a single type cleanly, our conveying systems service starts from exactly this comparison.
QUESTIONS WE HEAR
Which conveyor is best for fine powders?
For dry, fluidisable powders, an airslide is the cheapest and cleanest for downhill runs and a bucket elevator or screw for lifts; a pipe conveyor or an enclosed belt suits longer or more variable routes. Open belts are a poor choice for fine dry powders because of dust at transfers.
When is a screw conveyor better than a belt?
For short, enclosed or metered duties — feeding out of a hopper, linking two machines, handling hot or hazardous material — where simplicity and containment matter more than energy or wear. Over longer distances, with abrasive material or at high rates, a belt is usually better.
Can a belt conveyor go uphill?
Yes, up to the angle the material will hold on the cover — commonly in the 15–20° region for many bulk materials, less for rounded free-flowing ones, more with chevron or cleated belts. Beyond that, a pipe conveyor, a sandwich belt or a bucket elevator is the usual answer.
What is the most energy-efficient conveyor?
For horizontal transport the belt conveyor has the lowest energy per tonne of the mechanical types; the airslide is lower still but only for fluidisable powders on a downhill slope. Screw conveyors are among the least efficient because of friction between the material, the flight and the trough.
How do I choose between a pipe conveyor and a covered belt?
A covered belt still spills at transfers and cannot curve; a pipe conveyor contains the material fully, takes curves and can carry material on the return. If the route is straight and short and the material is not dusty, the covered belt is cheaper; if dust, spillage or route geometry are the problem, the pipe conveyor usually pays for itself.