Cost Effective Application Zones

SOCIETY FORMINING, METALLURGY,AND

EXPLORATION, INC.

PREPRINT, NUMBER

P.o. BOX 625002 . LITTLETON, COLORADO. 80162-5002

Cost- Effective EquipIllentApplication Zones

Bill MorganEquipment Application Consultant

Caterpillar Inc.,Peoria,IL 61629-2430

2

This paper discusses the economic zones of applicationfor several different types of earthmoving equipment:dozers. wheel loaders in load-and-carry applications,wheel tractor scrapers, articulated trucks, rigid-frametrucks and wagons. Only the medium to large pieces

of equipment were considered. From this chart(Figure 1), you can see the size range, in tons ofcarrying capacity, of Caterpillar equipment and thespecific models analyzed.

Figure 1

Dozers

~Load-and-Carry

~Articulated Trucks

~Scrapers

Rigid-Frame Trucks

~Wagons

2t 67t

~D8N D11N

2t 35t

IJB:E988F 994

20t 40t

~D400D

13t 52t

lIEEIC621E 633E 651El657E

35t 240t

E!i<. .769C 777C

85Tt 300+t

7938

..,"""""

""""

.

'

,

'

,.

'

,.

'

,.

'

,.

'

,

"

.

".

"

.

"."

.

",'.'. ....f'}".

,.""".

776C-WAGON

Capacity, Tons

Figure 2 shows the normal economic transport or hauldistance ranges for these various systems or types ofequipment. Let's explore why the different types andsizes of equipment have definite economic zones.

Figure 2

Dozing

Load-and-Carry

Scrapers

Articulated Trucks

Rigid-FrameTrucks

Wagons

OmOft

100m328ft

III

1000m3,280ft

I10000m32,800ftOne-WayHaulDistance

3

Earthmoving can be broken down into the following fivephases:I. PreparingII. LoadingIII. HaulingIV. DumpingV. Conditioning

These five phases need to be considered when lookingat the economics of earthmoving. The primary purposeof this talk is to look at the cost comparison of loading,hauling or transporting the material and finally,dumping it. The initial preparing of the material byblasting, ripping, adding water, or a variety of otheroptions as well as the final conditioning or placementof the material upon dumping was not considered.

The cost of loading and dumping the material is usuallyfairly constant regardless of the length of haul.Figure 3 shows some representative costs for load,dump and maneuver which are normally considered tobe the "fixed costs" of earthmoving. Figure 3 shows thecost-per-ton for a dozer, wheel loader (load-and-carry),self-loading scraper, push-loaded scraper, a medium-sized truck and a smaller articulated truck, both loadedby wheel loaders. Notice that the fixed costs generally

Figure 3Fixed Costs

Load,Dump& Maneuver$0.30

. LoadingMM Dump &

Maneuver

5 $0.20

~w00 $0.10

ascend over this range of machines. That is, a dozerhas the lowest fixed costs, while trucks generally havehigher fixed costs. Generally speaking, the haulingcosts are just the reverse. That is, trucks generallyhave lower hauling costs than scrapers, and scrapershave lower hauling costs than a wheel loader or adozer. This means that on short distances the dozerstarts with an advantage which it soon loses because ofits high hauling or transport cost.

Figure 4Haul Conditions Effect

Tons/Hourfor 657E/PPScraper1200

1000I-

::J 8000J:Us 600c0~ 400

200

0ft

(m)2000 4000 6000 8000 10,000 12,000(610) (1219) (1829) (2438) (3048) (3658)

One-Way Haul Distance

Let's use a self-loading 657 Push-Pull Scraper and lookat the effect of some of the hauling variables onproduction and cost per ton. Figure 4 shows productionin tons per hour versus haul distance from 300 feet(91 m) to 10,000 feet (3048 m) where the haul is level inone case and the grade is uphill 8% in the second case.The production hauling up the grade is substantiallylower than that hauling on the level, illustrating that thehauling conditions do have a substantial effect on the0

0 to 0'1 0'1 .... 0.... 0) C1I .... ,1:10.... .... .... 0'Z m. tn (1 0

"0 0"0

Hauler

4

production and the resulting cost per ton (which isshown in Figure 5). Generally, the most importantfactor to be concerned with is how far the material hasto be transported; the secondary effect is the haulingconditions over that distance.

Figure 5

$1.00

$0.80c0

S $0.60tn

8 $0.40 I

$0.20

Haul Conditions EffectCost/Ton for 657E1PPScraper

0ft

(m)2000 4000 6000 8000 10,000 12,000(610) (1219) (1829) (2438) (3048) (3658)


Another important factor can be some of the componentlimitations for different pieces of equipment. Forinstance, for all rubber-tired machines, tiretemperature limitations can be a problem. For the657E1PPScraper they can be quite severe depending onthe type of tires used. Figure 6 shows how theproduction of the 657E1PP Scraper has to be reduced

Figure 6

1200

1000

... 800~0:J:-:!! 6000I-

400

200

0ft

(m)

Tire Temperature Limitations657E1PPScraper- Push-Pull Loading

2000(610)

4000(1219)

6000(1829)

10,000(3048)

8000(2438)


with bias ply tires which have a limit of 225 ton mileper hour, and with radial tires which have a ton mileper hour limit of 527. It was assumed that themachines were working full bore - that is, they wereworking at a 50-minute hour for a continuous periodof time within the tire ton mile per hour limitation.Obviously, the radial tires have higher work capacitythan the bias ply tire. However, the radial tire mayormay not have the same capability of resisting cutting,etc. in rocky material. So the best choice of tiredepends on several factors including the ton mile perhour capabilities.

Figure 7 points out the cost-per- ton for the various tireconfigurations on the 657E1PPScraper with unlimitedproduction and the bias and radial ply tires. If cut-resistant bias ply tires have to be used to resist rockcutting, then the machine's performance has to belimited to a very short distance to prevent tireoverheating. The same general trend is true on anytype of rubber tired product. Usually trucks are limitedon much longer haul distances, and wheel loaders inload-and-carry applications could have tire overheatingproblems on much shorter distances.

Tire Temperature Limitations657E1PP Scraper - Push-Pull Loading

10,000(3048)

12,000(3658)

4000 6000 8000(1219) (1829) (2438)


12,000(3658)

Figure 7

$1.00

c $0.80

:g $0.60U

$0.40

$0.20

0ft 2000

(m) (610)

5

Let's look at dozers and wheel loaders on load-and-carryon relatively short distances. Here the dozeris limited to 300 foot (91 m) distances and the wheelloader to 500 feet (152 m). The bend in the cosVtoncurve for the 988F and 994 reflect the effect of tiretemperature limitations. The dozer has lower cosVtonon short distances. On longer distances the wheelloader shows lower costs. The way the material has tobe loaded and then dumped may have a significanteffect on the choice of these two types of equipment.

Figure 9 shows the cost-per-ton comparison forthe large dozer, the medium wheel loader, largepush-loaded scrapers and large self-loaded scrapers.You can see that the self-loading scraper is the mostcost-effective from 300-1000 feet (91-305 m). Themain reason why the self-loading scraper has theeconomic advantage in this distance range is the factthat it does not have the cost burden of the pusher (onthe short cycles only two or three scrapers can be usedwith one pusher).

Figure9 CostITon VS. Distance.Dozers vs. Wheel Loaders vs. Scrapers

$0.40r;

$0.30c:0 ,!;; $0.20.U) I'.00

$0.10

0ft

(m)200 400 600 800 1000(61) (122) (183) (244) (305)


1200(366)

Figure 10 compares the cost-per-ton for two self-loading scrapers (633E and 657E1PP) and two push-loaded scrapers (621E pushed by a D8N Tractor andthe 651 Push-Pull Scraper pushed by the D11N). Inboth cases, bigger is better. The 651 Scraper is themost cost-effective beyond 7000 feet (2134 m) and themost cost-effective scraper from 300-7000 feet (91-2134 m) is the 657E1PPSelf-Loading Scraper.

Prior to Figure 10, all of the machines have beenindependent units. That is, the dozer, the wheel loader(on load-and-carry) and the self-loading scrapers all areindependent of a loading tool. The 621 and 651 bothrequire assistance during loading with a push tractor.

Figure 8 CostITon VS. DistanceDozers vs. Wheel Loaders

$0.60 r

$0.50

5 $0.40

U) $0.300

0 $0.20

$0.1 0'

0ft 100 200 300 400 500 600

(m) (30) (61) (91) (122) (152) (183)

One-Way Haul DistanceFigure 10 CostITon VS. Distance

$0.80

c: $0.600

U)

<3 $0.40.

$0.20

0ft 2000 4000 6000 8000 10,000 12,000

(m) (610) (1219) (1829) (2438) (3048) (3658)


6

This brings in another factor to consider: the matchbetween the loading tool and the number of haulersthat can effectively work with that loading tool. As youmight imagine, the longer the haul distance, the longerthe hauling cycle time, and the more scrapers that canbe effectively worked with the pusher. In this analysis,the optimum number of haulers was used at any givenhaul distance to give the lowest possible cost per ton.[Caterpillar Fleet Production and Cost (FPC) softwarewas used to estimate the production and cost for all thescrapers, trucks and loaders while EarthmovingFundamentals (EMF) software was used for the dozers.]

Let's switch now to a comparison between the self-loading scrapers and articulated and rigid-frame trucksloaded by a 988F Wheel Loader. In this particularcase, the capacity of all three units is about the sameso the size effect is minimized in this comparison onFigure 11. The relative cost-per-ton of the two trucksloaded by the same loader are about the same on thisparticular set of hauling conditions. There are caseswhere the higher flotation and greater mobility of thearticulated truck would show a distinct edge over arigid-frame truck that uses a narrow, high pressuretire. This is one of the primary reasons why articulatedtrucks have a place in the different operating

Figure11 CostITon VS. Distance

Trucks vs. Scrapers vs. Dumpers$0.80

$0.60!:0

~(/) $0.4000

$0.20

0ft

(m)2000 4000 6000 8000 10,00012,000(610) (1219) (1829) (2438) (3048) (3658)


conditions. The 633E Self-Loading Scraper has adistinct economic cost advantage on the shorterdistances and the crossover is somewhere around8000 feet (2438 m) in this particular set of conditions.Beyond that distance the trucks would have theeconomic advantage.

How would the larger scrapers stack up against theeven larger trucks? Figure 12 compares the 651Epushed by a D11N, a 657E1PP Self-Loading Scraper, the35-ton 769C loaded by the 988F and finally an 85-ton777C loaded by the 14 yard 992D Wheel Loader. Thispoints out a general trend on the trucks that bigger isbetter - 85-ton truck having significantly lower costs-per-ton than its 35-ton counterpart and we see aneconomic crossover somewhere around 5000 feet(1524 m) between the self-loading 657E1PP Scraperand the 85-ton 777C. The economic crossover with the85-ton truck and push-loaded scraper is somewherearound 3000 feet (914 m).

Figure 12

$0.80

$0.60!:0

~ $0.40(/)00

$0.20

CostITon VS. DistanceTrucks vs. Scrapers

0ft

(m)2000 4000 6000 8000 10,00012,000(610) (1219) (1829) (2438) (3048) (3658)


7

Let's go one step further on the trucks and move allthe way up to the 793B 240-ton truck (one of the largesttrucks built in the world today) loaded by a 60 yardcable shovel. This team has a significantly lower cost-per-ton than the 85-ton 777C as shown in Figure 13.You will notice that the distance range has beenextended out to 25,000 feet (7620 m). The 240-tontruck class is now establishing a new benchmark in lowcost-per-ton for high quantity, long distance hauling.

CostITon vs. Distance

10,000 20,000(3048) (6096)


30,000(9144)

Wagons can generally pull more material than truckscan carry in good hauling conditions. Figure 14 showsa comparison of the same size truck - one with a bodyto carry the material- the 85-ton 777C, loaded by the992D compared to a 1SO-tonwagon pulled by the samehorse - the 776C in which the body has been replacedwith a hitch. On the very short distances, the lowerfixed costs on the piggy-back truck make it the mosteconomical package, but out beyond about 7000 feet(2134 m) the additional capacity of the 1SO-tonwagonshows a lower cost-per-ton. It should be mentionedthat the hauling conditions were very, very favorable inthis particular comparison with a very firm road and a -1% grade on the haul to represent very easy haulingconditions. If the conditions toughen up with higherrolling resistance or adverse grades, the wagon losesthe economic edge shown here.

Figure 14

$0.60

s:: $0.400

~tn00 $0.20

CostITon vs. DistanceTrucks vs. Wagons

0ft

(m)30,000(9144)

10,000 20,000(3048) (6096)


Figure 13

$1.20

$1.00

$0.80s::0

$0.60tn00

$0.40

$0.20

0ft

(m)

8

The discussion so far has concentrated on trying toshow the general economic distances for the variouspieces of equipment involved. Obviously, the equipmentchoice for a given set of conditions depends on manyother factors. Figure 15 shows cost-per-ton versus thefleet production in tons per scheduled hour for 35-150ton size trucks, all loaded by the best size wheel loader.For instance, Line D represents the production for the150-ton 785B Truck loaded by a 994 Wheel Loaderwhere the number of trucks working with the loader isshown as a dot. If you have too few trucks for a givenhauling condition, the cost-per-ton is going to be highand if you have too many trucks, which means trucksare waiting, the cost will also be high. For this

Figure 16

particular haul, the optimum fleet size is six trucks withthe one 994 - although the cost-per-ton with 4-5 trucksis almost as low. In this particular case, a productionrate of almost 2400 tons per hour was required and thesix trucks would just meet this production rate.Looking at the next smaller truck size (777C), Line Ashows the production with one 992D Loader and asecond loader is added for Line E. This shows how thefleet size can be increased to meet a given productionrate. In this particular example, nine of the 85-ton777Cs would be required with two 992D Loaders. Andthis also happens to be at the minimum cost-per-ton,but the cost-per-ton for the 85-ton truck is substantiallyhigher than that for the 150-ton truck.

Cost vs. Production$0.70

$0.60

$0.50

c

~ $0.40tn

<3 $0.30

$0.20

$0.10

01000 2000 3000

Tons/Scheduled Hour

/

9

SummaryThe economic haul distances for these various typesof equipment are best illustrated in Figure 2. Otherjob conditions, such as grades, underfoot conditionsor material appetite will influence you fmal choice.

Figure 2 I I !

Dozing

Figure 16 points out the general work envelope andsome important considerations for each type ofequipment. Select the equipment type first and then letthe quantity to be moved and the production raterequired dictate the size and number of equipmentrequired to most economically move that material.

Load-and-Carry

Wagons

Scrapers

ArticulatedTrucks

Rigid-FrameTrucks

OmOft

100m328ft One-WayHaulDistance

1000m3,280ft

10000m32,800ft

10

References

Journal Article1. Morgan, W.e., and Peterson, 1.1., 1968,

"Determining Shovel-Truck Productivity," MiningEngineering, Dec., pp 76-80.

SME Papers1. Dan Gove and Bill Morgan, 1994,

"Optimizing Truck-Loader Matching - UsingFleet Production and Cost to Optimize Truck-Loader Match."

2. John Wiebmer, SME Paper 93-256,"Different Horses for Different Courses."

Books/Papers1. Cummins, A.B., Given, LA., Connel, James P., 1973

"Truck Haulage," SME Mining EngineeringHandbook, Society of Mining Engineers,Vol. 2. pp 18-16 to 18-30.

2. John Ingle, 1993"Mobile Mining Systems Fundamentals,"International Mineral Development Sourcebook.

Software1. Fleet Production and Cost 2.0 (FPC), 1993 and

Earthmoving Fundamentals 2.02 (EMF) are availablethrough Caterpillar dealers. The FPC 2.0 single userorder number is SERD0344 and site license isJERD2045. EMF 2.02 order number is JERD2038.English is the standard language, but several otherlanguages are included. FPC and EMF arecopyrighted and proprietary to Caterpillar Inc.

Cost Effective Application Zones

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