Belt Conveying

The state of the art conveyor CV1103 at Wesfarmers NorthCurragh mine incorporates many innovative energy sav-ing features, such as intelligent, multi-speed VF drives, low

rolling resistance pulley cover rubber, large idler rolls and wideidler spacing. Chute designs are high efficiency and include aunique variable geometry design at the mid station drive tominimize dust and belt wear. The paper describes design andselection procedures for the custom designed belt with ultralow rolling resistance pulley cover, excellent crack resistanceand proven aging resistance. Final cost benefits of 41% operat-ing cost and 39% capital cost were achieved as a result of thisstate of the art design.

R.B. Steven, USAConveyor CV1103 at Wesfarmers North Curragh mine is the

worlds longest single flight conventional conveyor. The belt is 40

km long. Wesfarmers together with design and construction

contractors, Laing O’Rourke, were recently awarded the “Austral-

ian Bulk Handling Facility of the Year, 2007 (Resources and

Infrastructure)” for this $130 million project which is a model for

energy efficient conveyors.

Award-winning System features great Energy-savings

Belting the Worlds’ LongestBelting the Worlds’ LongestSingle Flight ConventionalOverland Belt Conveyor *

Fig. 1: Curragh North conveyorCV1103, view from head

* This article is based on a paper presented at the 9th ICBMH Conference at the University of Newcastle, NSW, Australia, October 11, 2007 [1,2].

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1. Introduction

The worlds longest, and possibly the world’s most sophisticatedconventional conveyor is located about 21 km north west ofBlackwater and 200 kmwest of Rockhampton. It runs for 20.3 kmtransporting coal from the new Curragh North open pit mine toa unique 5-way distribution point near the Preparation Plant.Owned and operated by Wesfarmers Curragh Pty Limited thisoverland conveyor was a joint venture design partnership be-tween Laing O‘Rourke, Australia (LOR) and Conveyor Dynamics,Inc., USA (CDI). LOR was the turn-key design, construct, supplyand commissioning contractor, CDI was the technology providerto LOR for major equipment specifications, dynamic analysis,control analysis and its integrated systemdesign, advanced chuteflow technology, and critical rubber compound parameters inassociation with Veyance Technologies, (Goodyear EngineeredProducts), to minimize rolling resistance.

The conveyor was part of the Curragh North Mine project ex-pansion which was first approved in 2003 and commissioned in2007. With four horizontal curves, smart multi-speed AC motordrives, variable geometry chute, 5m carry idler spacing, large di-ameter center roll idlers, super low rolling resistance rubber andrip detecting technology, the 20 km conveyor, CV1103, repre-sents the state of the art in modern conveyors, Fig. 1. The con-veyor has a haul road running parallel to it that was used beforethe conveyor was operational. However, at 2500 t/h the convey-or can deliver in 4 hours what it took the haul trucks to deliver inone day.

Compared to conventional conveyor technology the special fea-tures employed on CV1103 permit the use of a ST1500 instead ofa ST2500. This in turn permits lower rated structure and drivecomponents to be used. The new technology achieves cost sav-ing benefits in the order of 40% in both capital and operatingcosts compared to those of a conventionally designed conveyorWith four horizontal and twenty eight vertical curves (Fig. 2)CV1103 overland conveyor snakes over the ground transportingup to 2500 t/h of -32 mm coal at speeds up to 7.5 mps. The coalis discharged from the conveyor into a 500 ton capacity hopperwhich has the ability to direct its load towards one of five differ-ent destinations via a five-way chute.

The mechanical simplicity of the thin black rubber belt convey-ing the coal belies its complexity. With 5 m carry side and 10 mreturn side idler spacing the 16.6 mm thick belt supports almosthalf a ton of coal between each set of carry idlers. Fig. 3 showtypical idler configurations. High efficiency chutes, including aunique “smart” chute at the fixed tripper drive, Fig. 4, are em-

ployed. At the tripper drive the chute geometry automaticallychanges as the belt speed passes 75% of full speed.

Instead of fixed speed AC motors and fluid couplings the con-veyor is equipped with five ABB VF multi-speed drives whichstart the 1200 mm wide Veyance Technologies Flexsteel ST15007mm x 5mm belt in a smooth 400 seconds. The belt is driven bytwo carry side ceramic lagged 1000 kW drive pulleys at the headand two 1000 kW carry side and one 250 kW return side drivepulleys at the mid-point tripper.

Intelligence is programmed into the conveyor’s PLC drive con-trols enabling the belt to adjust its speed automatically to matchthe requirements of the coal demand. The belt stops automati-cally when the discharge hopper is full. The benefit is that nopower is wasted driving an empty belt. An empty belt of thislength can take in excess of 1000 kW to drive. This speed controlfeature on its own is a major contributor to the conveyor’s ener-gy saving. For example, for a conveyor without intelligent speedcontrol running 6,000 hours/year of which 25% is running empty(typical), the annual power costwasted running empty is $67,500per annum (assumes empty belt operating power of 1000 kWand $0.045 cost per kW.hr). With intelligent speed control thereare secondary benefits that arise due to

a) less belt pulley cover wear,b) longer idler life,c) longer lagging life,d) longer motor life,e) longer gearbox life, and.f) less pollution

Fig. 2: Plan view of conveyor CV1103 with four horizontal curves Fig. 3: Typical 10 m idler section. This belt length supports 0.93tons of coal with < 1% sag

Fig. 4: Smart variable geometry tripper chute

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Belt power demand has also been minimized by careful atten-tion to idler and belt design including idler spacing, idler geom-etry, idler bearings, idler roll diameters and pulley cover rubbercompound selection. The relative importance of each of theseparameters is critical to the final design. Asmany of these param-eters are temperature sensitive, each application’s geographiclocation has to be studied carefully and treated uniquely toachieve optimum energy savings. These parameters have beenthe subject of much research. Early contributors were HannoverUniversity [3], Delft University [4,5], and Conveyor DynamicsInc. (CDI), [6,7]. Most recently, the University of Newcastle haspublished data on the influence of idler roll diameters, idler spac-ing, belt speed, belt tension and bulk solid properties on the mo-tion resistance of conveyor belts [8].

In order to protect the belt investment, rip sensors are installedin the belt every 200 m. Veyance Technologies Sensor Guard2000 rip sensor detector heads are installed at the tail, mid-drive and head. Located on the Tropic of Capricorn, the Cur-ragh site is at the same latitude as the Kalahari Desert in Africa.Ambient site daytime temperature is over 40 °C in Decemberand January and the black body surface temperature of anybelt exposed to direct sunlight can get much hotter. To protectthe belt from direct sunlight CV1103 is covered for the entirelength of the conveyor, thus significantly reducing belt surfacetemperatures [9].

High ambient temperature conditions pose ageing issues for thebelt designer. In total, the challenges for the belt manufacturer inthis application can be summarized as follows

a) understand belt construction requirements for the systemdesign [12-17];

b) provide sufficient abrasion resistance to handle top and bot-tom cover wear [18,19];

c) minimize the rolling resistance;

d) understand the maximum rubber strain creating the poten-tial for surface cracking;

e) assess and allow for the rubber ageing characteristics for theapplication;

f) optimize splice efficiency to enable the use of reduced safetyfactors;

g) minimize the number of splices by maximizing belt lengthsthrough special packaging, see Fig. 5.

To begin with let’s look at some belt construction basics for astate of the art steel cord conveyor belt.

2. Steel Cord Belt Basics

2.1 Belt Construction

Fig. 6 shows a 3-D schematic of themakeup of a typical steel cordconveyor belt. Belt width and strength are determined from thesystem’s design requirements. Design tonnage, idler design, idlerspacing, pulley cover rubber rolling resistance, required splice ef-ficiency, and the selected safety factor will all influence the finalchoice. Belt construction is determined from the selected beltwidth, belt strength, required material abrasion, required rollingresistance, environmental conditions and the required life.

Fig. 7 shows the final construction chosen for Curragh’s CV1103belt after careful considerations as detailed in the sections below.

2.2 Steel Cords

80 cords of 4.6mm diameter, each with a minimum breakingstrength of 23.0 kN, were chosen for the CV1103 belt giving anominal minimum breaking strength of 1533 kN/m.

Cord construction is based on the required strength, flexibility,rubber penetration and field experience. The most commonconstruction for small diameter conveyor belt cords (less than6.0 mm diameter) is a 7 x 7, Fig. 8. illustrates the construction.Each filament color represents one filament diameter. For goodconveyor belt design the filament diameters are chosen suchthat there are gaps between them. These gaps are important toallow the rubber to penetrate between them. The rubber be-tween the filaments acts as an insulator and prevents one fila-ment fretting on another, and to prevent moisture migrationalong the cord from a belt cover damage point. Good rubberpenetration into the cord also significantly increases the dynam-ic fatigue life of the cord in service.

Fig. 9 shows laboratory equipment used to measure air penetra-tion of cords in a belt. 1 Bar pressure is applied to one end of a400 mm long belt sample and the pressure drop is measured

Fig. 5: One of the 40 racetrack reels Fig. 6: Anatomy of a typical steel cord belt construction

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over 1minute. Curragh’s CV1103 belt showed no loss of pressure,indicating excellent rubber penetration.

2.3 Top Cover

Top cover rubber is required to resist material abrasion and dete-rioration due to weathering or ageing. In the case of CurraghCV1103 a long belt life was sought for the belt which would beworking in a hot environment. Section 6.0, below, discusses indetail the work performed for the top cover of the CurraghCV1103 application.

2.4 Insulation Rubber

Insulation rubber surrounds the cords and is designed to providegood dynamic bonding to the steel cords and to the top and bot-tom cover rubbers for the life of the belt. It is also the rubber thatmust penetrate the cord filaments andprovide insulationbetweenthem. It also serves to hold the ends of the belt together in thesplice. Special tests are conducted to ensure that the rubbermeetsthese requirements, Figs. 10 and 11 which show the dynamic cordadhesion test and the dynamic splice efficiency test, resp.

For the Curragh belt a high performance insulation compoundwas used with 80,000 to over 100,000 cycles on the dynamic ad-hesion test (c.f. AS1333 10,000 cycles min.). Dynamic splice effi-ciency for CV1103 is greater than 63%.

The high splice efficiency permits the use of a lower operationalsafety factor. For CV1103 a safety factor of 5:1 (i.e. running ten-sion 20% of minimum nominal belt break strength) was selectedbased on a high friction condition, or 6.2:1 (i.e. running tension16% of minimum nominal belt break strength) based on a lowfriction condition.

2.5 Pulley Cover Rubber

Previous field studies [3] have determined that for long relativelyhorizontal overland conveyors belt indentation rolling resistanceis the dominant factor contributing to the power. Similarly, fieldstudies [6,10] have demonstrated that different grades of pulleycover rubber can significantly change the energy absorbed bythe indentation of the belt on the idler. Curragh’s CV1103 pulleycover rubber selection is discussed in Section 4.0, below.

Fig. 7: Schematic construction of Curragh 1200 mm Flexsteel ST1500 7 mm x 5 mm belt Fig. 8: Typical construction of 7x 7 cord

Fig. 9: Rubber penetration test equipment

Fig. 11: Veyance Technologies’ dynamic splice test [11]

Fig. 10:Dynamic cordadhesion test

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3. System Design Considerations -Belt Tensions

A common basis used for measuring and comparing conveyorefficiency is the DIN coefficient of friction, or friction factor, “ƒ”.This is defined in the standard DIN 22101 [12]. Based on fieldstudies the DIN standard suggests the friction factor of a typicalconveyor would be DIN ƒ = 0.020. It also suggests that a wellaligned conveyor with large (>159 mm) diameter idler rollswould have a DIN ƒ = 0.010, or DIN ƒ = 0.040 for a conveyorwith poor alignment and small (<108 mm) diameter idler rolls.

Belt tensions are typically calculated from well developed andtested conveyor design methodologies [12,13] and in the case ofCurragh CV1103, CDI design software which has been developedand refined overmany years was used [14]. Of primary interest inthis conveyor is the use of an energy efficient low rolling resist-ance pulley cover compound. Based on laboratory measure-ments for the special low rolling resistance pulley cover rubber ofthe belt developed for CV1103 the DIN Factor is anticipated tobe in the order of 0.0083 after an initial break-in period.

4. Rolling Resistance

Fig. 12 shows the results of one of the earlier published referencesto low energy or low rolling resistance belt studies performed byHannover University [3]. Their study examined the sources of re-sistances of a long overland conveyor based on field measure-ments. The dominant parameter is the indentation rolling resist-ance of the belt on the idlers. In this study, primary resistanceswere identified as indentation rolling resistance (61%), flexuralresistance of the bulk material (18%), secondary resistances, de-fined as resistances due to material acceleration, belt bending onpulleys, pulley bearings and scrapers (9%), bearing resistance ofthe idlers (6%), flexural resistance of the belt (5%) and extraordi-nary resistances, defined as misaligned training idler loads, etc.,(1%). Idler roll diameter was identified as a critical parameter inbelt rolling resistance [3-7]. Energy consumed by the belt rubberis proportional to (Roll Diameter)-2/3 [10]. That is, for example, a200 mm diameter idler roll will have 0.63 times the resistance of a100 mm roll. As the majority of the load sits on the center of thebelt there is more benefit from increasing the center idler roll di-ameter than the side rolls.This strategy was used very successfullyon Henderson’s P-2. For Curragh’s CV1103, in order to minimize

rolling resistance, a large 194 mm diameter center idler roll wasused with 178 mm diameter side rolls.

Since the ability of the belt’s rubber cover to influence rollingresistance was made known, conveyor belt manufacturers haveembarked on major low rolling resistance rubber developmentprograms and there have been many applications around theworld taking advantage of this technology [6,10,15,16]. For Cur-ragh, a super low rolling resistance rubber was developed by Vey-ance Technologies in conjunction with CDI to minimize powerfor the application.

4.1 Determination of an Optimum LRRCompound

Veyance Technologies’ approach was to evaluate a series of com-pounds using design of experiment (DOEX) techniques whereseveral ingredients were changed in a controlled fashion, com-pared with the physical test results and then a new improvedseries of compounds was developed based on the findings. Anoptimum compound was finally selected considering all data.Several parameters must be considered when evaluating a newcompound as typically there are trade offs. For example, as thelow rolling resistance property is improved other compoundphysical properties, or its processing ability may be compro-mised. In every case, a balance is sought where the best result ofthe primary, desired property is achieved with the least impacton secondary properties. The criterion used for rolling resistancein this study was the rolling resistance factor (RRF) where rollingresistance factor is defined as

RRF= tan δ____E’1/3

(1)

wheretan δ = E’’__

E’ (2)

andE’ = storage modulus [N/mm2]E” = loss modulus [N/mm2]δ = loss angle

The rolling resistance factor, RRF, is a single parameter that canbe used to compare the rolling resistance performance of differ-ent rubbers at a specific temperature, frequency and strain.

Fig. 12: Distribution of belt resistances on a long overland conveyor [3]

Fig. 13: Rolling resistance factor curves for first series of rubbercompounds evaluated

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Fig. 13 shows the RRF factor characteristic curves for the first se-ries of nine compounds evaluated together with that of the topcover compound (DIN X) for comparison. The target RRF was0.064 at -2 °C.

From this study, compound A-5 was selected as having the bestRRF and physical properties. Based on this, another series of ninecompounds (i.e. the ‘B’-series) were designed and tested. RRF forthe second series of test are shown in Fig. 14.

From the second group of compounds, B-1 to B-9, compoundB-1, which achieved a RRF of 0.0561 at -2.2 °C, had superior phys-ical properties and good processing properties was selected asthe primary compound for the Curragh pulley cover.

5. Idler Geometry and Maximum RubberStrains

With a 5 m idler spacing and a 45° troughing angle, it was of ma-jor interest to examine the idler geometry and assess the maxi-mum rubber strain in the idler junction area of CV1103. Therehave been several instances where conveyors with long idlerspans and/or large idler gaps have suffered premature service lifedue to idler junction failures. Although more common in pliedfabric belts these problems can occur in steel cord belts. In orderto assess this for the Curragh overland, a laboratory mock-up ofthe originally proposed idler configuration was made to assessthe belt-in-idler geometry.

It was determined from this simple laboratory rig that the centeridler roll width should be increased in order to avoid potentialbelt damage from the edge of the idler can. Such damage hadpotential to occur either during an abnormal running conditionor from a seized bearing situation as the conveyor ages.

In order to calculate the maximum rubber strain for CV1103 con-veyor a finite element analysis (FEA) of the loaded belt and idlergeometry was undertaken. For FEA model success, the materialproperties for all components must be determined very accurate-ly. The material properties of the steel components, such as theidlers and idler frame, are common and well documented. How-ever, those for rubber are unique to each rubber compound. Rub-

ber is a non-linear material, that is, the load required to deform itby a fixed distance changes in a non-linear way. Special two-di-mensional testing must be performed in order to establish the re-action of the rubber to each applied load for the load range underinvestigation.This unique relationship for each rubbermust be en-tered into the FEA model database before any analysis can bedone.The same is true for the steel cords which have amore linearbehavior, however, have a tendency to rotate about their principalaxis when a longitudinal load is applied.

Fig. 15 shows Veyance Technologies’s bi-axial test machine usedto establish the physical properties of the individual rubbersused in the Curragh belt.

From the system geometry and the rubber and steel cord mate-rial data an FEAmodel was generated. Figs. 16 and 17 show someof the FEA results for the belt in the idler region for the Curraghbelt operating at 2500 t/h and 7.5 mps. For the fully loaded beltthe study showed the maximum principal strain on the top cov-er was 3.73% and on the pulley cover was 4.19%.

Fig. 14: Rolling resistance factor curves for second series of rubbercompounds evaluated

Fig. 15: Veyance Technologies’ bi-axial test machine to determinerubber properties for FEA

Fig. 16:Rubber top cover

surface strains

Fig. 17:Rubber bottomcover surface

strains

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These maximum strain values are used to assess rubber fatiguelife based on crack propagation on the cover rubbers, discussedin section 7.2 below.

6. Rubber Ageing

6.1 Heat Ageing

Rubber ageing occurs as the rubber looses its oils and waxes(anti-ozonants and anti-oxidants) which migrate to the rubbersurface during the life of the belt. As it looses these compo-nents the rubber hardens and it looses its elasticity. One way toquantify the elasticity of a rubber is to measure the rubber’selongation before it breaks. Typically, a new rubber belt coverwill elongate 450% to 600% before it breaks. In service, theelongation at break will deteriorate over time and the rubber isconsidered to have reached its useful service life when its elon-gation has dropped to 150%. Depending on the rubber compo-sition and the ambient temperature this process normally takestens of years. However, like many processes, it is temperature

dependant and the deterioration in elongation is faster at high-er ambient temperatures.

In order to predict a rubber’s useful life it is possible to run ac-celerated laboratory tests at different elevated temperaturesthen apply the Arrhenius’s equation to predict service life at theambient temperature. The Arrhenius life prediction method iswell established in the rubber industry and has been field provenfor many rubber products.

The Arrhenius equation is given as

k = A·eE___R·T (3)

where

k = rate coefficient

A = constant

E = activation energy

R = universal gas constant

T = temperature in deg Kelvin

It should be noted that A and E are assumed not to vary withtemperature.

For the CV1103, several rubber cover samples in the form ofsmall 2 mm thick dumbbells were heat aged in ovens at 70, 80,90 and 100 °C (Fig. 18). At regular intervals samples were re-moved and tested to ASTM D378 for tensile strength and elon-gation. From this data values of k are determined for each testtemperature.

Plotting the values of k for the temperatures studied against theinverse of the temperatures generates the Arrhenius Plot. Fromthis the Arrhenius equation can be solved for the cover rubberunder investigation. This equation can then be used to predictthe change in rubber elongation for given service temperaturesover a given period of time.

Table 1 shows the Curragh site average daily temperature distri-bution for day and night for every month during the year. In ad-dition, it shows the average number of daylight hours recordedper day for eachmonth. From this information a predictive studywas made for both top and bottom cover rubbers for Curragh’sCV1103 belt using the Arrhenius equation developed for eachrubber. Fig. 19 shows the results.

Fig. 19 indicates that, based on applying the Arrhenius equationto the annual pattern of typical average daily temperature distri-bution, the predicted life for the top cover to reach 150% elonga-tion is 19.7 years and the pulley cover does not reach 150% after32 years.

Some studies have been made in the past to compare the Ar-rhenius equation prediction with data from conveyor belts thathave been run in the field, e.g., a 14 year old belt from the C-6conveyor at Rio Tinto’s Kennecott copper mine in Utah, USA,[20,21] and a 20 year old slope belt at the Thompson Creek mo-lybdenummine in Idaho, USA. In the first example the Arrhenius

MonthTemperature [°C] Daylight

HoursDay Night

January 34.3 21.5 13.2

February 33.2 21.2 12.9

March 32.0 19.6 12.2

April 29.5 15.7 11.5

May 25.9 11.6 11.0

June 22.8 8.5 10.7

July 22.5 7.1 10.8

August 24.8 8.2 11.3

September 28.3 11.9 12.0

October 31.7 16.1 12.6

November 33.7 19.0 13.2

December 34.7 20.7 13.6

Table 1: Site temperatures [22,23]

Fig. 18:Oven ageingof coversamples

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equation predicted an elongation of206% after 14 years for Kennecott’sC-6 against an actual 435%. In thesecond example, the Arrheniusequation predicted an elongation of200% after 20 years for ThompsonCreek’s slope belt against an actual395% cover elongation. The conclu-sion is that the Arrhenius equationprediction method for conveyorbelts is scientific but in practice isoften conservative.

6.2 Crack Propagation

In addition to heat ageing studies,crack propagation studies were per-formed on laboratory tests for thetop and pulley covers.

The Texus Flex Test, based on ASTMD 3629-99 is shown in Fig. 20. Thetest was originally developed as aprocedure to measure cut growth resistance of rubber com-pounds and was adopted as it has been shown in numerous in-stances to relate qualitatively to tire cut growth.The test involvesrepeatedly striking 25.4 mm x 31.8 mm x 4.8 mm thick rubbersamples against a bar at a known rubber strain. A transversesemicircular groove of diameter 4.78 mm is molded across thewidth of each rubber sample and the sample is pierced with a2.0 mm (0.08”) diameter pin which is tapered to a chisel point toprovide an initiation point for cracking. Periodically the test isstopped and a measurement is taken of the length of the crack.The crack growth rate at different rubber strain levels is then de-termined.

By mounting the rubber samples in slots on the periphery of arotating cylinder (400 rpm) the tester achieves a flex rate of 400cycles/min (6.7 Hz). The cylinder and striker bar are mountedinside an environmental chamber and the test is normally con-ducted at 40 °C to accelerate the test. The striker bar positionrelative to the cylinder is adjustable using an integrated verniermicrometer screw. This allows different stain levels to be set be-tween 0% and 41%. Normally multiple rubber compounds aretested at the same time with six samples of each compoundmounted at equal spacing around the perimeter of the driventest cylinder.

From the test results from three different test strain levels thetop cover crack growth rate is given by

y = 9·E - 24·x10.234 (4)

and for the Pulley Cover, the crack growth rate is given by

y = 3·E - 24·x10.594 (5)

where

y = crack growth rate (inches/cycle) and

x = maximum rubber stain (%)

In order to apply this knowledge to the Curragh CV1103 applica-tion we need to know the maximum surface strain and thenumber of times the rubber is flexed to this level. In the FEAanalysis above we determined that the maximum surface strainfor the fully loaded belt on an idler was 3.73% for the top coverrubber and 4.19% for the pulley cover rubber. For simplicity ofthe analysis we will assume that the belt sees these maximumstrain levels at every idler, including the return idlers. This is areasonable, though conservative assumption as the belt flexes inthe same sense on the return idlers as it does on the carry side.This is because of the turnovers and the 35° offset return idlers. If

Fig. 19: Predicted elongation vs time for the CV1103 cover rubber

Fig. 20:Texus Flex Tester

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we consider that the belt sees a total of 5,282 idler sets (sum ofcarry and return) in one revolution and that at 7.5 m/s the beltwill make 16.2 revolutions per day. Then, assuming the conveyordoes not stop for 365 days a year the belt will see a total of312,324,660 idler flexions in a 10 year period.

Based on Eq. (2) above, the estimated crack growth rate at 3.37%strain is 6.59 · 10-17 for the top cover and based on equation (3)the crack growth rate at 4.19% strain is 1.172 · 10-17 for the pulleycover. Applying this to the estimated number of idler flexions fora 10 year period, the estimated crack growth in service is 2.1 · 10-8 inches for the top cover and 3.7 · 10-9 inches for the pulley cover.This is acceptable.

7. Cost Considerations

Curragh’s CV1103 benefited from a number of new technologiesthat resulted in significant project cost savings.The combinationof large idler center rolls, low rolling resistance pulley cover, wideidler spacing and VF drives provided the following cost benefits:

a) lower belt cost (ST1500 instead of ST2500);

b) fewer idler sets (5,282 instead of 10,564);

c) smaller Drives (4,250 kW instead of 6,440 kW);

d) lower powered gearboxes;

e) lower rated structure;

f) no fluid couplings;

g) annual operational energy savings.

Table 2 summarizes the estimated cost savings for this applica-tion using the latest technologies discussed above comparedwith a conventional conveyor design. The values have been nor-malized to show as percentages of the total project cost over 10years for a conventional conveyor design.

Estimated operating cost savings are 41% of the con-ventional design and the estimated capital cost sav-ings are 39% of the conventional design.

8. Conclusions

Modern day long overland conveyors are competingwith state of the art truck and rail haulage to achievethe lowest cost per ton of material conveyed per kil-ometer. Their success depends on their efficient de-sign, their reliability and their low cost. The paper hasdiscussed some of the innovative design features usedon Curragh’s CV1103 conveyor tomake it both energyefficient and reliable. Capital and operating costs arefavorably impacted by large idler center rolls, 5 m and10 m idler spacing and the development of a superlow rolling resistance pulley cover compound. Beltwear is favorably impacted by both the top cover rub-ber selection, long term ageing properties and specialchute designs. Lower belt safety factors down to 5:1

were permitted with the used of a specialized insulation com-pound around the cords which can achieve 63% dynamic spliceefficiency. Estimated cost savings for the high tech conveyor de-sign are of the order of 41% lower operating cost and 39% lowercapital cost than a conventional conveyor design.

Based on rubber testing and predictive power calculation a DINFriction Factor for CV1103 was anticipated to be in the order of0.0083.

Crack growth study using a Texus Flex test predicted the esti-mated crack growth in service to be 2.1 · 10-8 inches for the topcover and 3.7 · 10-9 inches for the pulley cover. Cover ageing testsand the application of the Arrhenius equation were used to pre-dict service life. The criterion used was rubber’s elongation dete-rioration to 150% (due to oils and waxes that keep the rubberflexible being lost over time). The study predicted a life of 19.7years for the top cover rubber and in excess of 32 years for thepulley cover rubber.These estimates are ultra conservative basedon measurements of rubber cover elongation of conveyor beltstaken after 14 years and 20 years hard rock mining service inUtah and Idaho in the USA respectively.

The paper indicates the complexity involved in designing a beltfor amodern overland conveyor such as Curragh’s CV1103wherethe goal is maximum benefit for the customer. It also highlightsmany of the sophisticated features that make Curragh’s CV1103conveyor a flagship for state of the art conveyor technology onan international level.

Acknowledgements

The author would like to acknowledge the substantial work andsupport received from others during the course of this project. Inparticular, from K X and T A who were responsi-ble for the compound development and testing. From GML, who was responsible for the belt’s production andfor coordinating initial project involvement and site activities.From J Y, T A, and B M for FEA workand J P and M S for testing and data

StandardDesign

LRRDesign

Savings[%]

Operating expense

Energy 29 17

Total operating 29 17 41

Capital expense

Belt (ST2500 vs. ST1500) 23 19

Structure/motors/gearboxes etc 48 24

Total Capital 71 43 39

Total conveyor cost (10 years) 100 60 40

Table 2: Normalized project costs comparison to conventional designand savings. Total conventionally designed conveyor cost overa 10 year period = 100.

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analysis. From M H, who oversaw all activities, and fi-nally from CDI for advice regarding the system design and poweranalysis software.

References

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[3] H, M., and A. H: The Energy-Saving Design of Beltsfor Long Conveyor Systems; Bulk Solids Handling Vol 13(1993) No. 4, pp. 749-758.

[4] S, C.: The Calculation of the Main Resistance of BeltConveyors; Bulk Solids Handling Vol. 11 (1991) No. 4, pp.809-826.

[5] J, C.: The indentation of Rolling Resistance of BeltConveyors; Fördem und Heben Vol. 30 (1980) No. 4, pp.312-318.

[6] N, L.K.: The Channar 20 km Overland; Bulk SolidsHandling Volume 11 (1991) No. 4, pp. 781-792.

[7] N, L.K.: The Power of Rubber; Bulk Solids HandlingVol. 16 (1996) No. 3, pp. 333-340.

[8] W, C.: Design considerations for belt conveyors; Aus-tralian Bulk Handling Review, May/June 2007

[9] Conveyor Dynamics Inc.: Report measuring up to 30 °Clower surface temperatures on belt protected from directsunlight at Hamersley Iron’s Channar overland belt inWest-ern Australia.

[10] G, D.: Low Rolling Resistance for Conveyor Belts;International Rubber Conference, Melbourne, Australia2000

[11] DIN 22101: Test Procedure for Conveyor Belt Splices; Part 3,1993.

[12] DIN 22101: Belt Conveyors for Bulk Materials Basis for Cal-culation and Design; Aug. 2000.

[13] CEMA Handbook: Belt Conveyors for Bulk Materials; 6thedition, Conveyor Equipment Manufacturer’s Association,USA

[14] Conveyor Dynamics Inc.: Beltstat v 7.0; Bellingham, WA,USA

[15] K, W.: Henderson 2000; 2004 SME Annual Meeting,Denver, May 2004

[16] N, L.K.: Zisco Installs World’s Longest Troughed Belt15.6 KM Horizontally Curved Conveyor; BELTCON 9 con-ference, RSA, October 1997.

[17] L, R.: Local Stresses in Belt Turnovers in ConveyorBelts; BulkMaterial Handling by Conveyer Belt III, SME, Feb-ruary 2002.

[18] M, D.J., M.Z. S, and K.M. A: Ex-tending Conveyor Belt Life by Improving Abrasion Resist-ance; SME Annual Meeting, Phoenix, AZ, February 25-27,2002

[19] A, J.: Theoretical basis and industrial applicationsof energy-saving and increased durability belt conveyors;Acta Montanistica Slovaca, Rocnik 8 (2003) cislo 2-3,

[20] S, R.: Replacing C-6 Conveyor Belt at Kennecott Cop-per, Bingham Canyon Copper Mine; Bulk Solids HandlingVol 23 (2003) Special Open Pit Mining, pp. 26-35.

[21] S, R.: Study of C-6 Conveyor Belt at Kennecott Copper,Bingham Canyon Copper Mine; SME Annual Meeting, Feb2004

[22] http://www.worldclimate.com

[23] http://aa.usno.navy.mil/data

Robin Steven, USA

Dr Robin Steven holds a B.Sc. andPh.D. in Mechanical Engineeringfrom the Queens University of Bel-fast, Northern Ireland. He hasworkedfor Veyance Technologies Inc. (for-merly The Goodyear Tire & Rubber Company Engi-neered Products Division) since 1974. During his timewith Goodyear he has worked in several product areasincluding hose power transmission and conveyor belts.He also has experience working for several years inGoodyear plants around the world including NorthernIreland, South Africa, Brazil and the United States. He iscurrently Principal Engineer, Worldwide Conveyor BeltApplications, and Team Leader of Veyance Technology‘sFlexsteel® steel cord conveyor belt group based in Mar-ysville, Ohio.

Contact:Veyance Technologies Inc.13601, Industrial Parkway, Marysville, OH 43040, USATel.: +1 937 644 8909Fax: +1 937 644 8958E-Mail: robin_steven@veyance.com

About the Author

181bulk solids handling · Vol. 28 · 2008 · No. 3