Stockpile Segregation

Technical Paper T - 551

STOCKPILE SEGREGATION

By Jerry Nohl, P.E. and Bob Domnick

T - 551 Stockpile Segregation

CONTENTS

ABSTRACT ............................................................................... 2STOCKPILING .......................................................................... 2STOCKPILING PROBLEMS ..................................................... 3PROBLEMS CAUSED BY SEGREGATION .............................. 3CAUSES OF STOCKPILE SEGREGATION .............................. 4WHEN IS STOCKPILE SEGREGATION A PROBLEM? ........... 6DEALING WITH SEGREGATION.............................................. 7PREVENTING SEGREGATION ................................................ 7THE WINDROW CONCEPT.................................................... 10TELESCOPING CONVEYORS ............................................... 11PARTIALLY DESEGREGATED PILE....................................... 15FULLY DESEGREGATED PILE .............................................. 18STOCKPILE VOLUME ............................................................ 20SUCCESS WITH AUTOMATION ............................................. 20CONCLUSION ........................................................................ 21

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ABSTRACTMaterial segregation is a problem that is inherent to most stockpiling tech-

niques. As the demand for a higher quality product increases, the problem ofstockpile segregation becomes more significant. Telescoping radial stackingconveyors are known to be the most effective solution for stockpile segrega-tion. They are capable of creating a stockpile in layers, with each layer consist-ing of a series of windrows of material. In order to create a stockpile in thismanner, the conveyor must be in motion almost continuously. Although themotion of a telescoping conveyor can be controlled manually, automation is byfar the most effective method of control. An automated telescoping conveyorcan be programmed to create customized stockpiles of many different sizes,shapes, and configurations. This nearly unlimited flexibility can add efficiencyto an overall operation, as well as provide a higher quality product.

STOCKPILINGEach year contractors spend millions of dollars to produce aggregate prod-

ucts that are used for many different applications. Among the most popularapplications are base material, asphalt, and concrete. The process of creatingthe products for these applications is very complex and costly. Tighter specifi-cations and tolerances mean that the importance of product quality is becom-ing more and more significant.

There are many phases to the process of aggregate production. The virginmaterial must be stripped or blasted from its original location within the quarry.Once the material is removed from the mining surface, the process of reduc-tion begins. The original material is first run through a primary crusher to re-duce the product to a manageable size that can be handled by conveyors.Next, the material is run through a secondary crusher and possibly a tertiarycrusher to reduce the product size even further. Along with the various crush-ing operations, the product is also passed through vibrating screens to sort itby particle size. Once the material has been sorted into different sized prod-ucts, it is then ready to be stockpiled for storage. Eventually, the material isreclaimed from the stockpile and transported to a location where it will be incor-porated into a road base, asphalt product, or concrete.

The equipment required for stripping, blasting, crushing, and screening is veryexpensive. However, todays equipment is capable of consistently producingaggregate material that is within specifications. Stockpiling may seem to be atrivial part of aggregate production; nevertheless, if done incorrectly, stockpil-ing can cause a perfectly in spec product to become out of spec. This is tosay that some of the cost of creating a good product can be wasted by usingpoor stockpiling techniques.

Although placing product in a stockpile endangers its quality, stockpiling is avital link in the aggregate production process. Stockpiling is a storage methodthat ensures material availability. The rate of production often differs from therate at which the product is required for a given application, and stockpiles helpto absorb this difference. Stockpiles also allow contractors sufficient storage torespond effectively to fluctuating market demands. Because of the benefitsoffered by stockpiling, it will always remain an important part of the aggregateproduction process. Therefore, producers must continually improve their stock-piling techniques in order to reduce the risks associated with stockpiling.

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STOCKPILING PROBLEMS

The three most common stockpilingproblems are segregation, degradation,and contamination. The primary focusof this paper is on segregation. Segre-gation is defined to be the separationof material by particle size. Differentapplications of aggregate products re-quire very specific and consistent gra-dations of material. Segregationcauses excessive variation in the gra-dation of a product.

Segregation can occur virtually any-where throughout the process of ag-gregate production after a product hasbeen crushed, screened, and blendedto its proper gradation. The first likely place for segregation to occur is withinthe stockpile (Figure 1). Once the material has been placed in the stockpile, itwill eventually be reclaimed and transported to a location where it will be used.The second place that segregation can occur is during handling and transport.Once on site at an asphalt or concrete plant, the aggregate material is placedin feed hoppers and/or storage bins from which the product will be withdrawnand used. Segregation can also occur when hoppers and bins are filled andemptied. After the aggregate is blended into an asphalt or concrete mix, seg-regation can also take place during the application of final mix to a road orother surfaces. Segregation can be a problem in many different areas; how-ever, the emphasis of this paper will be on causes and solutions for segrega-tion within the stockpile (Figure 1).

PROBLEMS CAUSED BY SEGREGATIONA uniform aggregate product is essential to producing high quality asphalt or

concrete. The fluctuating gradation of a segregated aggregate product makesit nearly impossible to produce an acceptable asphalt or concrete product. Agiven weight of smaller particles has a larger total surface area than the sameweight of larger particles. This presents a problem when combining the aggre-gate into an asphalt or concrete mixture. If the aggregate contains too high ofa percentage of fines, there will be a shortage of concrete paste or asphalt,and the mixture will have an overly stiff consistency. If the aggregate containstoo high a percentage of large particles, there will be an excess amount ofconcrete paste or asphalt, and the mixture will have a runny consistency. Roadsconstructed with segregated aggregate product will have poor structural integ-rity and, ultimately, a shorter life expectancy than those made from a properlydesegregated product.

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CAUSES OF STOCKPILESEGREGATIONThere are many factors that contrib-

ute to segregation within a stockpile.Since most stockpiles are created witha belt conveyor, it is important to un-derstand the inherent effects of a beltconveyor on the gradation of a mate-rial. As a belt carries material alongthe conveyor, a slight bouncing mo-tion is created by the belt rolling overthe idlers (Figure 2). This is due tothe slight sag in the belt between eachidler. This motion causes the finer par-ticles to settle to the bottom of thematerial cross section on the belt, andthe coarser particles to stay on the topof the material cross section (Figure3). Bridging of the coarse particlescauses them to remain on top.

Once the material reaches the con-veyor discharge pulley, it is alreadysomewhat segregated with the coarsermaterial on top and the finer materialon the bottom. As the material beginsto travel around the curvature of thedischarge pulley, the top (outside) par-ticles travel at a greater velocity thanthe bottom (inside) particles (Figure4). This difference in velocity thencauses the larger particles to travelfarther from the conveyor before land-ing on the stockpile and the smallerparticles to drop closer to the conveyor.Furthermore, the fine material has agreater tendency to cling to the con-veyor belt and not be discharged untilthe belt has continued further aroundthe discharge pulley. This causes evenmore fines to be pulled back to thefront side of the pile.

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When the material lands on the stockpile, the larger particles have a greaterforward momentum than the smaller particles. This causes the coarse mate-rial to continue moving down the side of a pile more so than the fines. Anymaterial, regardless of size, that cascades down the side of a stockpile is calledoverrun (Figure 5). Overrun is one of the leading causes of segregation in astockpile and should be avoided if at all possible. As overrun begins to tumbledown the slope of a pile, the larger particles tend to roll down the entire lengthof the slope while the finer material tends to settle into the side of the pile(Figure 5). Therefore, as overrun proceeds down the sides of a pile, fewer andfewer fines remain with the tumbling material. When the material reaches thebottom edge, or toe, of the pile, it consists primarily of the larger particles. Theeffect of overrun causes a pronounced segregation that is visible in a sectionview of a stockpile (Figure 6). The outer toes of the pile consist of the coarsermaterial, while the inner and upper portions of the pile consist of more fines.Particle shape also contributes to the effects of overrun. Particles that have asmooth or round shape are more likely to roll farther down the slope of a pilethan crushed particles that typically have a boxier shape. Overrun can alsocause material degradation. As the particles tumble down the side of the pile,they rub against each other. This abrasion can erode some of the particles intosmaller sizes.

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Wind is another cause of segrega-tion. After material leaves the con-veyor belt and begins its descent tothe stockpile, wind will affect the tra-jectory of different size particles.Wind has a great effect on fine ma-terial but little or no effect on largermaterial (Figure 7). This is due tothe fact that the surface area-to-weight ratio is greater for small par-ticles than it is for large particles.

WHEN IS STOCKPILESEGREGATION A PROBLEM?The potential for segregation within

a stockpile may vary depending onthe type of material being stockpiled.The most significant factor relatedto segregation is the degree of varia-tion of particle size within the mate-rial. Materials with a greater varia-tion in particle size will have a higherdegree of segregation when stock-piled. A general rule of thumb is thatif the ratio of the size of the largestparticles to the size of the smallestparticles exceeds 2:1, stockpile seg-regation is likely to be a problem(Figure 8). On the other hand, if theratio of the particle sizes is less than2:1, stockpile segregation will beminimal (Figure 9). For example, aroad base material which contains particles all the way down through200 mesh particles is likely to seg-regate when stockpiled. However,segregation will be insignificantwhen stockpiling a product such as washed stone. Sand can usuallybe stockpiled without a segregationproblem due to the fact that mostsand is produced wet. The moisturecauses the particles to cling to-gether, preventing segregation.

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DEALING WITH SEGREGATIONThere may be times in which seg-

regation was not prevented when theproduct was stockpiled. The outsideedges of a finished pile consist pri-marily of coarse material and theinner portion of the pile has a higherconcentration of fines (Figure 6).When reclaiming from the end faceof this type of pile, scoops must betaken from various locations in or-der to blend the material (Figure 10).Reclaiming only from the front faceor back face of the pile will result inall coarse material or all fine mate-rial.

There is also an opportunity for fur-ther segregation when loading atruck. It is important that the methodused does not result in overrun. Thefront of the truck should be loadedfirst, then the back, and finally themiddle. This will minimize the effectof overrun within the truck.

PREVENTING SEGREGATIONMethods of dealing with segregation

after the building of a stockpile areuseful, but the goal should be to pre-vent or minimize segregation as thestockpile is made. Mixing the stock-pile, building the stockpile in layers,telescoping conveyors, variableheight conveyors, radial travel con-veyors, rock ladders, telescopingchutes, and paddle wheels are alluseful in the prevention of segrega-tion.

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When building a stockpile with a truck,care should be taken to dump intoseparate piles to minimize overrun(Figure 11). A loader should be usedto push the pile together by raising thematerial to full bucket height anddumping, which will blend the mate-rial. Building larger piles should notbe attempted if it requires the loaderto drive on and degrade the material.

Building the stockpile in layers canminimize segregation. This type ofstockpile can be built with the aid of adozer (Figure 12). If material isbrought to the stockpile with a truck,the dozer should push the materialinto inclined layers. If the stockpile isbuilt with a conveyor, the dozer shouldpush the material into horizontal lay-ers (Figure 13). In either case, careshould be taken not to push materialover the edge of the pile. This resultsin overrun, which is one of the leadingcauses of segregation.

There are several disadvantages tomaking a stockpile with a dozer. Twosignificant risks are degradation andcontamination of the product. Heavyequipment continuously running overthe product will compact and crush thematerial. Using this method, produc-ers must be careful not to degrade theproduct too much in an attempt to al-leviate the segregation problem. Theextra labor and equipment requiredoften make this method cost prohibi-tive and results in producers settlingfor methods of dealing with segrega-tion upon reclaim.

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A radial stacking conveyor will helpminimize the effects of segregation(Figure 14). As the stockpile is beingbuilt, the conveyor moves left and rightradially. The end toe of the pile, whichis normally coarse material, will becovered with fine material as the con-veyor travels radially. The front andback toe will still be coarse material,but the stockpile will be blended morethan a conical pile.

There is a direct relationship betweenthe height of free fall of material andthe degree of resulting segregation.The fines are separated more andmore from the coarse material as theheight increases and the trajectory offalling material widens. Therefore,variable height conveyors are anothermethod of minimizing segregation(Figure 15). During the initial stages,the conveyor should be in the lowestposition. The distance from the headpulley to the pile should always beminimized.

Free fall from the conveyor onto thepile is another cause of segregation.A rock ladder will minimize segrega-tion by eliminating the free fall of thematerial. A rock ladder is a structurethat allows the material to flow downa series of steps onto the pile. This iseffective, but has limited application.

Segregation caused by wind can beminimized with a telescoping chute. Atelescoping chute at the discharge pul-ley of a conveyor that extends from thepulley to the pile will shield the windand limit the effects of it. If designedcorrectly, it can also limit free fall ofmaterial.

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As discussed previously, there is already segregation on the conveyor beltprior to reaching the discharge point. Also, further segregation occurs as thematerial leaves the belt. Paddle wheels may be installed at the discharge pointto re-blend this material. The rotating wheel has wings or paddles on it thatintersect and agitate the trajectory of material. This will minimize segregation,but the material degradation may not be acceptable.

Significant costs may be incurred as a result of segregation. Out-of-spec pilesmay lead to penalties or rejection of entire stockpiles. If out-of-spec material isdelivered to a job site, the penalty may be in excess of $0.50/ton. The labor andequipment cost to rebuild an out-of-spec pile is often cost prohibitive. The costper hour of using a dozer and operator to build the stockpile is higher than thatof an automated telescoping conveyor, and the material may be degraded orcontaminated in the effort to maintain the proper gradation. This will decreasethe value of the product. In addition, there is an opportunity cost associatedwith using equipment such as a dozer for a non-production task when it hasbeen capitalized for a production task.

THE WINDROW CONCEPT When creating a stockpile in an application where segregation can be a prob-

lem, another method can be used to minimize the effects of segregation. Thisinvolves making a stockpile in layers, with each layer consisting of a series ofwindrows (Figure 15). In a section view of a windrow stockpile, each windrowappears as a miniature pile (Figure 16). Segregation still occurs within each individual windrow from the same effectsdiscussed earlier. However, the segregation pattern is repeated more oftenthroughout the cross section of the pile. Such a pile is said to have a greatersegregation resolution because the segregated gradation pattern repeats it-self more often in smaller intervals. When reclaiming a windrow pile with afront-end loader, there is no need to blend the material because one scoopincludes several windrows (Figure 17). As a windrow pile is being reclaimed,the individual layers are clearly visible (Figure 18).

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Windrows can be created using dif-ferent techniques of stockpiling. Onemethod is to use a bridge and tripperconveyor system, though this alterna-tive is feasible only for stationary ap-plications. One significant disadvan-tage of stationary conveyor systemsis that they are typically fixed in height,which can result in segregation bywind as discussed earlier.

Another method is to use a telescop-ing conveyor. Telescoping conveyorsare typically preferred over stationarysystems because they can be relo-cated when necessary, and many areactually designed to be road-portable(Figure 19).

TELESCOPING CONVEYORSThe most effective way to build a

windrow stockpile is by using a tele-scoping conveyor. The telescopingconveyor consists of a conveyor(stinger conveyor) mounted inside anouter conveyor of similar length (Fig-ure 20). The stinger conveyor has theability to move linearly along the lengthof the outer conveyor, thereby varyingthe location of the discharge pulley.The height of the discharge pulley isvariable as well as the radial positionof the conveyor. The three-axis varia-tion of the discharge pulley is essen-tial in making the layered pile that over-comes segregation.

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A cable winch system is often used toextend and retract the stinger conveyor.The radial movement of the conveyormay be driven by a chain and sprocketsystem or hydraulic powered planetarydrives. The height of the conveyor isoften varied via cylinders that extend atelescoping undercarriage system. Allof these movements must be controlledin order to build a layered pile automati-cally.

The telescoping conveyor has themechanisms in place to build a com-pletely layered pile (Figure 21). Mini-mizing the depth of each layer will helpto limit segregation. This requires theconveyor to be moving constantly as it

builds the stockpile. The need for constant movement makes automa-tion of the telescoping conveyor essential. There are several differentmethods of automation, some of which are less costly with significantlimitations, while others are fully programmable and offer much versatil-ity when building a stockpile.

One method of automation includes limit switches that control the mo-tion of the conveyor. As the conveyor begins to build the stockpile, itmoves in a radial direction while conveying material. The conveyor movesuntil a limit switch mounted to the axle of the conveyor is tripped by atrigger that is in its radial path. This trigger is placed according to thelength of the arc the operator wants the conveyor to travel. At this pointthe stinger conveyor extends a predetermined distance and starts trav-eling in the other direction. This process continues until the stingerconveyor has been extended out to its maximum extension and the firstlayer is complete (Figures 22 & 23).When the second layer is built, the stinger begins retracting from its

maximum extension, traveling radially and retracting at the arc limits.Layers are built until a tilt switch mounted at the discharge pulley isactivated by the pile.

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The conveyor will raise a predeter-mined distance and begin its secondlift. Each lift may consist of severallayers, depending on the rate at whichthe material is being conveyed. Thesecond lift is built similar to the first liftand so on until the entire pile is built.A large part of the resulting pile is de-segregated; however, there is overrunon each edge of the pile. This is be-cause the conveyor cannot automati-cally adjust the limit switches or thelocation of the objects used to tripthem. The retract limit switch must beadjusted so the overrun does not burythe conveyor axle. Another limitationdeals with the fact that it takes thesame amount of time to travel theouter arc as the inner arc (Figure 21).Since the outer windrow is muchlonger than the inner windrow, the ratethe discharge pulley moves with re-spect to the ground is much faster onthe outer windrow than the inner wind-row. Assuming constant conveyingcapacity, the layer will be higher on theinner arc than the outer arc (Figure24).Another method of automation con-

sists of utilizing a programmable logiccontroller (PLC) to control operationsof the conveyor. A PLC is a computerthat receives data from input devicesand processes this data to control theoperation of various components. Anencoder can be mounted to the winchthat extends and retracts the stingerconveyor. As the conveyor extendsor retracts, the PLC is aware of theexact location of the stinger conveyor,making its movements programmable.The extension and retract limits of thestinger can be automatically changedfor each layer. By making each sub-sequent layer narrower, overrun canbe eliminated (Figure 24). The retractlimit can be adjusted so the axle doesnot get buried by overrun. The extendincrements can be shortened as theconveyor approaches the outer arc.This will result in a level pile at con-stant conveying capacity (Figure 25).

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An encoder can also be mounted toone of the wheels of the conveyor tomonitor the radial position of the con-veyor. The encoder for the radial traveldoes not rely on off-board devices toactivate switches. Instead, the en-coder is self-contained and can beprogrammed to adjust the arc limitsto eliminate overrun on the ends of apile (Figure 26). A tilt switch is mounted at the dis-charge point on the stinger conveyorto indicate at what point the conveyormust raise to the next lift. This en-sures that the conveyor will raise be-fore burying the discharge pulley in thepile. Some automation packages al-low the tilt switch to indicate when tomove one radial increment, rather thantravel continuously, which gives theability to build a desegregated pilewhen conveying capacity is not con-stant.

This method of automation lends it-self to customized automation pack-ages. The arc pile is by far the mostcommon (Figure 21). The arc pile isbuilt of windrows that are concentricto the conveyor feed point. In certainsituations, it is advantageous to cus-tomize the program. At some job sites,it is more convenient to load-out par-allel to the conveyor. In this case aninline pile would be desired (Figure27). The inline pile is built of wind-rows that are radial to the conveyorfeed point. It is a small matter to pro-gram the telescoping conveyor to buildthis type of a stockpile. Unusual sitelayout or lack of real estate could bereasons to choose a rectangular pile(Figure 28). In each instance, properreclaiming methods are not compro-mised.

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Customized automation extends be-yond stockpiling. When loading a railcar or vessel a linear pile is needed.Conventional radial stacking convey-ors cannot build the pile. However, atelescoping conveyor with an encoderon the winch can be programmed tobuild the pile (Figure 29). In the pastthis type of pile would have had to bebuilt by a stationary system with mul-tiple conveyors.

Automation options are not limited tothose listed above, as new processesand user expectations will be revealedin time. The automated telescopingconveyor is currently the most versa-tile tool in stockpiling, and will continueto be the most adept at meeting thesenew processes and expectations.

PARTIALLYDESEGREGATED PILE The windrow method of stockpilinggreatly reduces segregation, but over-run can still be a problem if the propermethod is not used (Figure 5). Thisoccurs when a lift of windrows is aswide as the lift below it. Material ineach lift must be prevented from roll-ing over the edges of the previous liftand creating overrun in order to mini-mize segregation completely. If over-run is not prevented, certain portionsof the stockpile will still be subjectedto segregation, and a partially deseg-regated pile will be created.

The bottom lift of a windrow pile cre-ated with a telescoping conveyor isapproximately as wide as the lengthof the telescoping section of the con-veyor (Figure 30). When the secondlift of windrows is created, overrunbegins to occur when the telescopingconveyor reaches its extension limitsand is making the innermost and/oroutermost windrows. Material spillsover the edge of the first lift and rollsdown to ground level, creating over-run (Figure 31).

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The same problem occurs when making the third lift. Again, as the telescop-ing conveyor reaches its maximum extension, material spills over the edge ofthe second lift and rolls down the back side of the pile to ground level (Figure32). This problem continues to worsen as the pile gets higher because theslope down the side of the pile gets longer (Figure 33). When a partially desegregated pile is completed, the final result is a stockpilethat consists of up to 40% overrun (Figure 34). Segregation has been essen-tially eliminated in the windrowed portion of the pile; but the effects of segrega-tion remain significant in the portion of the pile made up of overrun. In order tominimize overrun, the actual stockpiling process must be altered to create afully desegregated pile.

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FULLY DESEGREGATED PILE In order to eliminate overrun in a layered windrow pile, the extension limitsmust be changed for each lift. By changing the limits of travel of the telescop-ing portion of the conveyor, each lift of windrows can be made slightly smallerthan the lift underneath of it (Figure 26). The bottom lift of a fully desegregated pile is created the same way as a par-tially desegregated pile. The dimensions of the bottom lift are identical. Asmentioned before, the base of the pile is approximately as wide as length of thetelescoping section of the conveyor (Figure 35). The stockpiling process begins to differ in the second lift by changing the ex-tension and retraction limits of the telescoping portion of the conveyor (Figure36). Both of the limits are changed by an amount A . This adjustment preventsmaterial from being discharged from the conveyor over the edge of lift 1. Thisessentially eliminates overrun.

When creating the third lift of the stockpile, the extension and retraction limitsare adjusted again by amount A (Figure 37). These adjustments preventmaterial from spilling over edge of the second lift and rolling down the front andback of the pile to ground level.

For each subsequent lift, the extension and retraction limits are adjusted toprevent overrun on the front and back of the pile (Figure 38). The limit adjust-ments actually decrease the distance that the telescoping portion of the con-veyor travels. As the number of lifts increases, the telescoping distance de-creases. This causes each lift of windrows to be narrower than the lift under-neath it.

The cross section of a fully desegregated pile is completely made up of wind-rows, and overrun is eliminated (Figure 39). Pile volume is sacrificed whencreating a fully desegregated; however, the quality of the material in a fullydesegregated pile is significantly better than that in a partially desegregatedpile, due primarily to the absence of overrun.

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Overrun is also created on the ends of a stockpile created by a telescopingradial conveyor. This overrun can be eliminated if adjustments are made to thelimits of radial travel of the conveyor. To prevent overrun on the ends of astockpile, the total radial arc must be decreased inward for each layer.

STOCKPILE VOLUME The stockpile volumes of a fully desegregated and partially desegregated stock-pile differ greatly (Table 1). A pile built with a conventional (non-telescoping)radial stacking conveyor is shown for comparison and is designated as areaR1. The axle on a telescoping conveyor is placed closer to the feed point thanthat of a conventional radial stacking conveyor. Because the stinger conveyoris able to retract, the operator is able to stockpile back to the axle. This result-ing pile is partially desegregated and is the highest volume pile as indicated byareas R1+R2 (Figure 40). The conventional pile has the next highest volumebut is segregated and is indicated by area R1. The fully desegregated pile hasthe lowest volume but is free of overrun and is indicated by area R3 (Figure 40).The factor that affects the volume of a fully desegregated pile is the extensiondistance. By maximizing that extension distance, the fully desegregated pilevolume is maximized and the towing length of the conveyor is minimized.

SUCCESS WITH AUTOMATION Automation is significantly changing many industries as it can offer a means ofachieving higher productivity and higher quality products in many different typesof operations. Although automation can prove to be the best method of control-ling a given operation, there are often several factors that seem to cause someapprehension with automated systems.

One of the biggest factors is simply the fear of change; especially a changefrom an existing system that seems to work well to a system that is much morecomplex. In many cases, the original system may have been a relatively simplepiece of equipment, but controls, sensors, and electronic devices are requiredto incorporate automation. The complexity of an automated system often in-timidates a user because of the inability to troubleshoot and fix problems thatmay arise. It is essential that the manufacturer have a good customer serviceprogram to assist users with service and maintenance on their systems. Thisincludes the ability to provide good technical support over the phone and to becapable of responding immediately to the need for parts or a field service tech-nician.

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Another concern that users may feelis that they are not capable of learn-ing how to operate an automated sys-tem. The key to overcoming these at-titudes is for the manufacturer to pro-vide excellent training for the users. Itis also important to provide goodoperators manuals and reference ma-terials that give clear operation instruc-tions.

Finally, automation components often have the perception of being delicate and unable to withstand theharsh environments inherent to many applications. As technology has progressed, suppliers of automationcomponents have considered these factors and addressed the vastly differing needs. For example, there areliterally thousands of different sensors available today, and each is designed for a specific application. Ulti-mately, it is the responsibility of the designers and manufacturers of an automated system to select the rightcomponents for the right application. This requires designers and engineers to be well aware of user expec-tations, application, environment, and what is available in terms of automation components.

CONCLUSION

In conclusion, automation is clearly the way to build a fully desegregated stockpile. An automated telescop-ing conveyor is the most effective method of minimizing segregation. It will save money and time whileproviding a better product. The equipment and labor costs of alternative stockpiling methods are higher, andequivalent product quality is unattainable by these other methods. The automation technology availabletoday provides exciting opportunities both now and in the future to maximize the production of high-qualityaggregates while reducing or eliminating labor-intensive operations. This will give the producer the ability tomake a product that will always meet increasingly stringent specifications.

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Stockpile Segregation