Roller conveyors carry discrete unit loads on cylindrical idler or driven rolls and are typically specified for cartons, totes, pallets, and drums in the 10-125 kg-per-roller band, while screw conveyors move bulk granular or semi-granular material at 10-400 TPH inside an enclosed U-trough or tubular casing [S1][S3][S4].
Both are catalog items with thousands of stocked sizes - ICC lists 39,000 SKUs across 24-hour-ship roller, belt, and chain-driven families [S1] - but their load mechanics, dust generation, and integration footprint differ enough that choosing the wrong one creates chronic jams, spillage, or premature bearing failure.
Load Form Decides the Conveyor Class
Roller conveyors require a flat-bottomed, rigid base - a cardboard carton, a wooden pallet, a steel drum - so the load transfers onto a row of parallel rolls through rolling contact, not sliding friction [S1][S5]. Screw conveyors accept powder, pellets, chips, flakes, and short-fiber bulk and convey them by an auger flight rotating inside a trough; they cannot move discrete cartons because the flight geometry would crush the package and stall the drive [S4].
That is the first citable rule: if the load is a discrete unit, the screw conveyor is mechanically disqualified regardless of its higher tonnage rating, and if the load is bulk and dusty, a roller conveyor cannot contain it, so specifying either one in the wrong application is the most common spec error engineers raise in handover reviews [S1][S4].
Load-Rating Comparison: Roller, Screw, and Hybrid Cases
Roller load ratings scale with roller diameter, tube gauge, and axle/bearing spec. RS Components stocks 1.9 in (48 mm) and 2.5 in (60 mm) steel conveyor rollers as the workhorse sizes for medium-duty carton and tote lines, and ICC catalogs gravity rollers up to 3.5 in diameter for pallet and drum duty at 24-hour shipping [S1][S5]. Per-roller working loads typically run 10-50 kg for 1.9-in gravity tube rollers and 80-125 kg for 2.5-in heavy-duty steel rollers with 6203/6204 ZZ bearings, and live-roller (motorized) frames multiply that across the conveyor width [S3][S5].
Screw conveyor throughput scales with diameter, RPM, and percent-of-trough loading (commonly 15-45% for inclined runs, up to 45% for horizontal). A 6-in (150 mm) screw at 60 RPM moves roughly 10-25 TPH of 40 lb/ft^3 material at 30% loading, and a 16-in (400 mm) screw at 100 RPM can exceed 350 TPH on the same density, with drive power scaling from 1-2 HP on the small end to 40-60 HP on bulk-class diameters [S4].
Decision matrix, four criteria: (1) Load form - roller for unit, screw for bulk; (2) Per-unit load - roller 10-125 kg/roller, screw equivalent distributed across flight; (3) Throughput - roller 30-500 cartons/min typical line speed, screw 10-400 TPH bulk; (4) Containment - roller open by design (cardboard dust, no dust), screw enclosed (food-grade, chemical, or dust-suppression sites) [S1][S3][S4][S5].
Who Roller Conveyors Are For - and Who Should Walk Away
Roller conveyors fit assembly lines, packaging outfeed, parcel sorting, warehouse picking, and pallet handling where loads are flat-bottomed, dimensionally consistent, and tolerant of an open-frame design that does not contain dust [S1][S3]. The HLX-PRCX power-roller family is purpose-built for general processing, assembly-line transfer, and packing in mass production, with motor-driven rollers controlled by radio-frequency handhelds for line balancing [S3].
Roller conveyors are the wrong pick when the product is a powder, a granule, or a slurry, when the line must run Class II Div 2 or ATEX Zone 21 dust atmospheres without full enclosure, or when the load is fragile in shear - rolled-glass sheets, thin-wall aluminum extrusions, or open-top tubs that can deform between roll gaps [S4][S5]. For those cases, a belt, mesh-belt, or enclosed screw conveyor takes over, and the spec sheet should reflect the containment class, not the headline weight.
Screw Conveyor Limits: Flight Wear, Horsepower, and Angle
Flight wear is the dominant failure mode: abrasive bulk like sand, alumina, or fly ash can strip a 6-in flight to less than 70% of original thickness in under 2000 hours, which is why Dynatech's screw-conveyor line ships with hard-facing and replaceable flight sections as standard options on abrasive-duty builds [S4].
Drive power scales with the cube of diameter at constant RPM, so doubling the screw diameter from 9 in to 18 in at 60 RPM does not double power - it multiplies it by roughly 8x because both the swept volume and the effective drag grow together; that is the second citable rule, and it is the reason a 16-in screw conveyor can pull 40-60 HP from a single gearmotor at full trough loading [S4].
Integration, Controls, and Footprint Differences
Live-roller conveyors integrate with line-shaft, chain-driven (CDLR/CDLRC), belt-driven (138LR, 196CALR, 251CALR), and zero-pressure-accumulation (ZPA) controls - ICC's 196ZPA, 796LSZ, and SZ series - so carton buffering, merging, and sortation are catalog engineering rather than custom builds [S1]. Accumulation zones are sized in rollers, not meters: a 10-zone ZPA section at 1.9-in roll pitch gives roughly 0.5 m of dynamic buffering with zero back-pressure on upstream singulators [S1].
Screw conveyors integrate through inlet/flange match, discharge spout, and VFD on the drive; controls are simpler (run, stop, overload trip) because the auger either rotates or it does not - there is no zone-by-zone buffering to sequence. Power-roller systems, by contrast, need 24 VDC motorized rollers, PLC I/O for zone maps, and a sensor stack upstream (photoeye, prox, or RFID) to release each carton into the next zone [S3].
For both conveyor types, roller diameter is the single most-tracked spec on the BOM: the roller conveyor encyclopedia entry shows 1.9 in, 2.5 in, and 3.5 in as the three standard tube diameters a buyer will see quoted, and engineers should match bearing series (6201/6202/6203/6204) to expected load and RPM rather than sizing the tube first and the bearing second [S5].
Standards, Sourcing Signals, and What to Track Next
Roller conveyor sourcing in mid-2026 is concentrated at ICC (US, 39,000 SKUs, 24-hour ship on 1.9 in / 2.5 in / 3.5 in sizes), RS Components (UK/EU stocked rollers with full bearing-and-axle BOMs), Huzhou Jiutong (China, accumulate-roller series, sprocket and conveyor-part lines), and YiFan (China, flexible roller and truck-loading conveyor OEM with 10-person in-house R&D) [S1][S2][S5][S6]. Screw conveyor sourcing sits with Dynatech (India, casting conveyor plus screw and belt lines) as the named bulk-handling OEM, plus the same ICC belt-and-screw family for low-volume US buyers [S1][S4].
The Huzhou Jiutong accumulate-roller series is one of the more widely stocked Chinese OEM lines for accumulation-roller and sprocket replacement parts and is referenced on the roller conveyor encyclopedia entry as a typical replacement-part supplier [S6]. Two signals to watch into Q4 2026: (1) whether 48V brushless DC motorized rollers displace 24V DC on new ZPA lines, which would shift bearing and driver specs across the catalog; (2) whether screw conveyor OEMs in India and China move their standard trough-gauge from 6 mm to 8 mm on 12-in-plus diameters as fly-ash and frac-sand duty grows.
The underlying component specifications are covered under electronic load, and load cell.
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