The horizontal-motion conveyor offers several ad-

vantages over other types of conveyors used for

transporting bulk materials horizontally during

processing. A horizontal-motion conveyor can

smoothly and efficiently move a huge variety of ma-

terials, such as polymers, hot potash, borax crystals,

potato chips, and breakfast cereal, without damag-

ing, segregating, stratifying, or aerating them. This

article answers common questions about horizon-

tal-motion conveyors and how to apply them.

The horizontal-motion conveyor (also called a hori-zontal differential-motion conveyor, differentialmotion conveyor, or differential conveyor) uses a

two-cycle slow-advance–quick-return motion tosmoothly convey any free-flowing bulk material horizon-tally. The conveying surface, which can be an open pan ora fully closed conduit, is a seamless, one-piece unit. Dur-ing the advance cycle, the conveying surface movesslowly forward. As it does, the material remains at relativerest on the conveying surface, even as it’s being movedforward. During the return cycle, the conveying surfacemoves quickly back to its original position and slips be-neath the material, in much the same way as a tablecloththat’s quickly jerked out from under a table setting. Thisdifferential action is continually repeated, giving the hori-zontal-motion conveyor the ability to smoothly conveymaterials as fast as 40 fpm over distances up to 200 feet.

Along with the differential motion, the horizontal-motionconveyor’s overall mechanical simplicity gives the con-veyor several advantages over other conveyors, such as vi-brating, drag, belt, screw, and pneumatic conveyors. Thehorizontal-motion conveyor has no moving parts otherthan its sealed drive unit. This reduces safety risks andsimplifies cleaning and maintenance. The conveyor alsohas intrinsic advantages for applications that require dustcontrol, reliable and gentle handling of fragile materials,and more. The following questions and answers providemore detailed information about the horizontal-motionconveyor’s capabilities and applications.

1Can the horizontal-motion conveyor transportmaterials at an incline?

Yes. Although the horizontal-motion conveyor is morecommonly used in horizontal applications, it can also beused in applications that require transport at a slight inclineor decline. The physical characteristics of the materialbeing moved determine the practical incline. Some parti-cle shapes will convey better up inclines than others. Forexample, round or spherical particles tend to roll and loseconveying energy on inclines.

When transporting fine material at an incline, materialtraces might be left behind on the conveyor pan at the pro-duction run’s end, requiring the pan to be cleaned. How-ever, the conveyor can be equipped with pan-cleaningdevices to handle this problem.

Answers to 12 common questions abouthorizontal-motion conveyors

Matt Mayo, Tim Talberg, and Paul Cichanowski Triple/S Dynamics

As appeared in Copyright CSC PublishingPBEJanuary 2012 www.powderbulk.com

Finally, the material travel rate and resulting conveyor ca-pacity will also be lower when conveying material at an in-cline. The drop in capacity can be countered by increasingthe conveyor’s operating stroke or pan width.

2Can this conveyor handle a change indirectional flow?

When properly configured, the horizontal-motion con-veyor can be used to convey either forward or backward— but only in one direction at a time. Reversing the drivemotor’s voltage polarity through the motor’s starter willreverse the flow direction, which can be useful in manyapplications. For example, say you want to package a ma-terial in both 50- and 100-pound bags. You could set up thehorizontal-motion conveyor so that the material was deliv-ered to the conveyor’s midsection. By reversing the flowdirection, you can then use the same conveyor to delivermaterial to bagging stations at each end of the conveyor.It’s also possible to equip the horizontal-motion conveyorwith an optional online reversing mechanism that allowsit to reverse flow nearly instantaneously.

3Can the horizontal-motion conveyor be totallysealed?

Whether you need to control dust, provide pressure isola-tion, blanket your material with an inert gas, or provideother environmental controls, the horizontal-motion con-veyor is readily adaptable. You can equip the conveyorwith a totally enclosed conduit instead of an open con-veyor pan. The conveyor can also have both a sealed sec-tion and a separate section (or sections) open to theupstream or downstream process (or both processes).

The horizontal-motion conveyor can also be adapted forapplications that don’t require a totally sealed system butstill need some dust control or isolation from the plant environment.

An open-pan horizontal-motion conveyor can be fittedwith a cover (with cleanout ports, if needed). Inlet and out-lets between two conveyors or between a conveyor andanother machine can be connected using a standard flexi-ble boot connection or, because of the unique sliding ac-tion of the horizontal-motion conveyor, by very closelymating the conveyor pan to the other conveyor or ma-chine. The latter leaves a very small distance for the mate-rial to travel from one machine to the other, which helpscontrol dust.

4What if multiple inlets and discharges arerequired?

A single horizontal-motion conveyor can readily incorpo-rate multiple inlets and outlets. Multiple inlets can be usedto introduce materials from different storage vessels or tometer several materials onto one conveyor. Because of theconveyor’s slow-advance, quick-return cycling, materialsneither mix nor separate during transport. If the inlets de-liver blended materials, they’ll stay blended; if they intro-duce the material in layers, it will stay in layers.

The horizontal-motion conveyor can also be fitted withmultiple lanes so that a single conveyor pan and drive unitcan be used to transport different materials.

One or more discharge outlets can be located at any pointalong the conveying section’s bottom to distribute the ma-terial. Each outlet can be fitted with a mechanical dis-charge gate to start and stop material discharge. Thesegates, typically pneumatically actuated, can be slide gates,butterfly valves, or tip-style drop gates.

Individual discharge outlets can be set up to distributevariable amounts of the total flow, ranging from “all” to“none” and anywhere in between. The conveyor can also

Some of the largest horizontal-motion conveyorshandle scrap metal, like this one weighing in at350,000 pounds and transporting up to 600,000pounds of metal per hour.

be designed to accumulate a predetermined amount of ma-terial before each discharge for an immediate delivery dur-ing demand. This capability is useful in applications suchas discharging into packaging scale feeders.

5Is this conveyor suitable for large-capacity,heavy-duty applications?

Horizontal-motion conveyors more than 200 feet long withpan widths up to 10 feet have been used successfully formany years. In applications requiring the conveyor to carryenormous loads of heavy materials such as scrap metal,structural trusses and impact beds are incorporated into theconveyor and the conveyor pan is constructed of abrasion-resistant plate metal 1 inch or more thick. As a result, theconveyor can handle massive impact loads and carryingcapacities. One such horizontal-motion conveyor weighsin at more than 350,000 pounds and its conveyor pan —117 feet long, almost 8 feet wide, and 3 feet deep — movesmore than 600,000 pounds of scrap metal per hour.

6Can the horizontal-motion conveyor handlematerial being fed from a full hopper?

Yes, the horizontal-motion conveyor has tremendousload-carrying capability. Some units can convey as muchas two to three times their own empty weight. Unlike a vi-brating conveyor, the horizontal-motion conveyor isn’t“detuned” by typical increases in material loading on theconveyor pan. What’s more, because it isn’t a “tuned” sys-tem, the horizontal-motion conveyor can be operated atvariable speeds to control the material’s travel rate.

7Can this conveyor be used to meter product?

A properly designed horizontal-motion conveyor can beset up to accept material from a full hopper and meter itwithout any intermediate equipment, such as a rotaryvalve. The discharge rate can be controlled by varying theconveyor’s motor drive speed. Because the conveyor canhandle deep material bed loads, the conveyor pan can alsofunction as a self-discharging storage unit.

In addition to metering material, the horizontal-motionconveyor can be equipped to provide product aligning,singulating (separating multiple rows of individual prod-ucts or pieces from a mass), or deshingling (producing asingle layer of product from a mass or stack of product).For example, a food processor making chocolate-coveredpretzels was using a vibrating conveyor in its productionline. The vibrating conveyor — which uses a vertical

pitching motion to move material forward — was shin-gling (stacking) the pretzels. However, the processor hadto assign several operators to manually align and deshin-gle product downstream from the conveyor. By replacingthe vibrating conveyor with a horizontal-motion conveyorequipped with aligning lanes and special deshinglingramps, the processor reduced labor costs and increasedproductivity. What’s more, the new conveyor significantlyreduced the number of pretzels damaged by shingling.

You can further regulate discharge from the conveyor panby installing pneumatically actuated dams or manually ad-justable flow baffles on the conveyor to accumulate andmeter material to other downstream equipment. Whenequipped with dams or baffles, the horizontal-motion con-veyor’s gentle motion eliminates product degradation andenables the conveyor to accumulate large amounts of ma-terial like snack foods or breakfast cereals behind the damsand baffles.

8Will the horizontal-motion conveyor work wellwith abrasive materials?

Yes; in fact, the horizontal-motion conveyor performsmuch better than a vibrating conveyor in terms of mainte-nance and overall conveyor wear. A vibrating conveyor’smotion presses the pan against the material, inducing agouging action that abrades the pan surface. Abrasivewear to the horizontal-motion conveyor’s conveyor pan istwo to four times less than that in a vibrating conveyor.

Recently, an industrial minerals producer was looking fora conveyor to handle fine, abrasive rock. The producer’smajor concerns were dust control and limiting conveyordowntime for maintenance resulting from abrasive wear.A horizontal-motion conveyor was designed for this appli-

This horizontal-motion conveyor pan is fittedwith multiple lanes that can singulate productsduring transport or transport different materialsfrom multiple inlets to the same destination.

cation with a fully enclosed conveyor pan with integraldust covers and was constructed of an abrasion-resistantmaterial with a Brinell hardness number of 400. Dustemissions were eliminated and, after 14 months of opera-tion, the conveyor pan showed an average surface wear ofjust 0.010 inch. The only maintenance the conveyor re-quires is periodic lubrication.

In another application, a ceramic parts producer had a dif-ferent problem: The dust generated from a cutting processwas causing the bearings on the producer’s existing beltconveyor to fail quickly. Maintenance access to the bear-ings, which ran the length of the belt conveyor, was diffi-cult and cumbersome. The producer replaced the beltconveyor with a horizontal-motion conveyor. Because theconveyor’s entire drive unit could be located at the con-veyor’s end and is enclosed, the unit’s moving parts aren’texposed to dust. The drive unit is also much easier to ac-cess and requires less frequent maintenance service.

The horizontal-motion conveyor can also be adapted fortransporting chemically corrosive materials, such as chlo-rinated bleach powder, by fabricating the conveyor panfrom a corrosion-resistant material, like titanium.

9Can moist or sticky materials be conveyed onthe horizontal-motion conveyor?

The horizontal-motion conveyor will work for a moist orsticky material, provided you use the right materials for theconveyor pan or use a liner with it. For example, for some ma-terials, such as powdered dishwashing detergent, a conveyor-pan liner made of ultrahigh-molecular-weight polyethylenewill prevent sticky particles from adhering to the surface.

The material’s gliding action over the conveyor-pansurface discourages material buildup.

10What about applications in which theconveyor will be exposed to very high orvery low temperatures?

The horizontal-motion conveyor is highly adaptable andcan be operated across an extremely wide range of temper-atures. In some applications, air or water cooling systemshave been used to enable a horizontal-motion conveyor toreliably handle hot materials up to 1,700ºF.

11Can the horizontal-motion conveyor beeasily cleaned?

This question comes up often, especially from processorsin the food industry and other industries in which sanita-tion is of utmost importance. Because of the way it’s con-structed, the horizontal-motion conveyor is typicallymuch easier to clean than other conveyors.

Because the horizontal-motion conveyor commonly con-sists of a one-piece, seamless conveyor pan riding on sus-pension points spaced periodically along its length, boththe pan’s interior and exterior surfaces can be easily ac-cessed for wipe-down cleaning. There are no supportframes or springs under the conveyor pan (which wouldintroduce cracks, crevices, and other dirt-holding sur-faces) that need to be cleaned. The material’s gliding ac-tion over the conveyor-pan surface discourages materialbuildup. In fact, the material’s continuous sliding action onthe conveyor’s surface typically scours the pan clean. As aresult, less cleaning time is required between productioncycles than with other conveyors.

When the horizontal-motion conveyor is totally enclosed(in either a rectangular or tubular shape), the unit isequipped with a clean-in-place (CIP) system. The CIP sys-tem uses water nozzles located at intervals along the con-

When totally enclosed, the horizontal-motionconveyor is commonly designed with a clean-in-place system that allows quick wet-cleaningbetween production runs.

veyor’s length so an operator can wet-clean the interior be-tween production runs.

12Is this conveyor energy efficient?

Very much so. The horizontal-motion conveyor uses lessenergy than a slider-belt conveyor and substantially lessthan a screw conveyor. The horizontal-motion conveyor isvery competitive with roller-belt, vibrating, and drag con-veyors in energy consumption.

One reason the horizontal-motion conveyor is so energy-efficient is that the drive motor, which is sized to start thedrive, typically draws a full power load only duringstartup. The rest of the time, the motor usually runs at 50percent or less of its rated capacity. (For most materials,the motor load is independent of the amount of materialconveyed.) The exception is for applications that requireconveying very heavy materials, like scrap steel or cast-ings. Then, increasing material loads will increase themotor’s amp draw. PBE

Matt Mayo and Tim Talberg are sales engineers and PaulCichanowski is an applications engineer at Triple/S Dy-namics, 1031 South Haskell Avenue, Dallas, TX 75223; 214-828-8600, fax 214-828-8688 (sales@sssdynamics.com,www.sssdynamics.com). Together they have more than 50years experience working with horizontal-motion convey-ors.