Spread Borough

Inclined Troughed Belt Conveyor Systems for Underground MassMining Operations

J C Spreadborough1 and A G L Pratt2

ABSTRACTInclined troughed belt conveyors are more frequently being selected froma range of alternatives, which include shafts and trucks for ore haulage inunderground mass mining projects. Belt conveyor haulage systems arebeing operated with lifts exceeding those normally associated with truckhaulage systems and approaching the limits of shaft haulage systems.

A belt conveyor haulage system, in this context, incorporatessubsystems for:• crushing,• tramp detection and removal, and• haulage.

This paper presents details of recent inclined troughed belt conveyorsystems for underground mining operations, and explores the applicationof inclined troughed belt conveyors for the increasing demands of futureunderground mass mining projects.

INTRODUCTION

The selection of haulage systems for underground mines hasfocused on shaft haulage, trucks and belt conveyors. Theapplication of these alternatives in the Australian mining industryis summarised in Figure 1 as a graph showing lift (m) versusannual production (kt/a) (Pratt, 2005). Troughed belt conveyorsare shown to be applied in the range to 8 Mt/a and 1200 m lift.

This paper further defines the current range of application oftroughed belt conveyor systems, defines limits on their applicationand the scope for increasing these limits to the demands of futureunderground mass mining projects. This paper does not address

the application of cable belt conveyors, though similar principalscan be applied to define their limits of application.

TROUGHED BELT CONVEYOR SYSTEMS

An underground conveyor haulage system will, in general,incorporate subsystems for:

• crushing,

• tramp detection and removal, and

• haulage.

Each of these subsystems will incorporate resources andfacilities for:

• monitoring and control, and

• maintenance.

The satisfactory performance of the haulage system isdependent on the performance of each subsystem and on theperformance of the resources and facilities provided formonitoring and control and maintenance.

The crushing subsystem is required to reduce run-of-mine(ROM) material to a size suitable for loading to haulageconveyors.

A typical crushing station is depicted in Figure 2.The tramp detection and removal subsystem is required to

remove tramp materials from the material stream and henceprevent tramp damage to haulage conveyors.

The tramp detection and removal subsystem will incorporateconveyors, tramp magnets, metal detectors and in some cases,facilities for manual tramp removal in a configurationappropriate for the size, shape, magnetic properties and quantityof tramp anticipated. The demands on the tramp detection andremoval equipment vary with the ground conditions and miningmethod. Poor ground conditions necessitate a greater utilisation

Tenth Underground Operators’ Conference Launceston, TAS, 14 - 16 April 2008 71

1. Associate Director, Maunsell Australia, 10 Finchley Street, MiltonQld 4064. Email: [email protected]

2. MAusIMM, Group Manager Mine Engineering, Newcrest MiningLimited, Level 8, 600 St Kilda Road, Melbourne Vic 3004.Email: [email protected]

FIG 1 - Operating ranges for underground haulage systems.

of rock bolts, straps and mesh for ground support. The blockcave method generally requires ground support only at theundercut and extraction levels. Ground support generallycontributes the majority of the tramp in the ore stream. Othercontributors include drill consumables, Load-haul-dump (LHD)bucket hardware and chute liners.

The haulage subsystem (Figure 3) includes the chutes, skirts,belt, idlers, pulleys, drives and structures that support andtransport the material from the feed point to the discharge point.The haulage subsystem may incorporate more than one conveyorflight and more than one transfer point.

Critical elements in the haulage subsystem include:

• Feed chute of dimensions appropriate for the materialreceived to direct the material on centre and in line with thereceiving belt.

• Belt to support the material and to transfer tractive forces tothe material. The belt carcass and the associated splicesprovide tensile strength. The belt covers provide protection forthe carcass and splices from impact, abrasion and corrosion.

• Idlers to support the belt.

• Pulleys to resist belt tensions at changes of direction and totransfer tractive forces from the drives to the belt.

• Drives to provide driving and braking tractive force and inertia– the driving and braking controls provide for minimumdynamic effects when starting and stopping, and for nomaterial retained in the transfer chutes for all stoppingscenarios, including emergency and power failure stops.

• Take-up to provide belt tension for no slip at the drives andfor belt sag control.

72 Launceston, TAS, 14 - 16 April 2008 Tenth Underground Operators’ Conference

J C SPREADBOROUGH and A G L PRATT

FIG 2 - Typical crushing station.

FIG 3 - Typical haulage conveyor head end.

• Holdbacks to prevent reverse movement, each capable ofholding 150 per cent of the load applied by the conveyor(AS1755) also able to withstand extreme events (drivesstalled in reverse, or belt locked, drives stalled, resultant belttension resisted by the holdback).

The monitoring and control functions are required to confirmcorrect operation and to initiate warnings or shut down in theevent of malfunction to prevent injury and equipment damage.

Devices are typically provided at the haulage subsystem fordetection of:

• belt drift,

• drive slip,

• belt rip,

• belt carcass and belt splice deterioration,

• take-up over-travel,

• equipment over-temperature, and

• emergency.

Maintenance equipment at the haulage subsystem willtypically include:

• monorails and/or cranes at drives and pulleys for change-outor repair;

• belt clamps to resist belt tensions when installing ormaintaining the belt (spring applied, hydraulic release, testedfor holding capacity);

• belt reel handling facilities; and

• belt splicing/repair facilities.

CURRENT APPLICATIONSTroughed belt conveyors are applied over a wide range oflength/lift combinations, but at the limits are grouped as long(overland) or high lift conveyors (Figure 4). Troughed beltconveyors for mass mining operations frequently fall into thesecond (high lift) group.

Troughed belt conveyors are also applied over a wide range ofmaterial flow rates, belt widths and belt speeds (Figure 5 andTable 1).


INCLINED TROUGHED BELT CONVEYOR SYSTEMS FOR UNDERGROUND MASS MINING OPERATIONS

RevengeCadjebut

Gordonstone DriftRidgeway Trunk

Mc Arthur River

Kapok

Nifty CV3

Ridgeway PortalChuquicamata

Prosper Haniel

Lafarge Surma

KPCChannar

Dawson CV-193Crinum Curragh North

-200

0

200

400

600

800

1000

0 5 10 15 20 25

Length (km)

Lift

(m)

High Lift

Long (Overland)

FIG 4 - Length/lift for typical long (overland) and high lift troughed belt conveyors.

RevengeCadjebut

Gordonstone DriftRidgeway Trunk

Mc Arthur River

KapokNifty CV3

Ridgeway Portal

Chuquicamata

Prosper Haniel

Lafarge Surma

KPCChannar

Dawson CV-193Crinum Curragh North

-200

0

200

400

600

800

1000

0 1000 2000 3000 4000 5000 6000

Feed Rate (t/h)

Lif

t(m

)

FIG 5 - Productivity ranges for typical long (overland) and high lift troughed belt conveyors.

LIMITS OF APPLICATION

The slope of the high lift group is limited by the slope of the driftor decline/incline in which the conveyor is mounted. This isnormally in the range 1:5.3 to 1:5.4 (10.5° to 10.7°) where thedevelopment is carried out using rubber-tyred equipment.

Length and lift are limited by the belt carcass construction andthe strength of the belt splice. These limits of length arepresented in Figure 6 for the Ridgeway Portal configurationoperating at 840 t/h, 3 m/s and with a splice factor of safety(FoS) of 6.7 for belt constructions in the range ST500 to ST7100.

The choice of belt construction is also limited by thetroughability of the belt. Troughability is the ratio of the crossbelt sag to belt width and generally reduces with increases incarcass strength. Reduced troughability results in poor belttracking and hence edge damage and/or tripping on belt drift.

FUTURE APPLICATIONS

Advances in future designs will be fundamentally linked to theload-carrying capacity of the available belt constructions andsplice designs. It is useful to recognise a parameter that is used tocompare wire rope constructions. This parameter is called thefree length and is defined as the length at which a rope will breakunder its own weight. It is calculated by dividing the ropestrength by its weight per unit length.

The free length of a range of steel cord belt constructions ispresented in Figure 7. The free length calculation recognises:

• loss of strength at the splice,

• free length of bare cords (reduces with increases in carcassstrength), and

• self weight of rubber in the carcass and in the covers.



Conveyor Material Length (m) Lift (m) Rate (t/h) Speed (m/s) Belt spec

High lift

Prosper Haniel Coal 3745 783 2000 5.5 1400 ST7500

Chuquicamata CB002 Hard rock 4578 540 5500 6.0 1830 ST10 000

Ridgeway Portal Hard rock 2863 503 840 3.0 1050 ST5500

Nifty CV3 Hard rock 2324 408 500 3.9 900 ST3150

Kapok Hard rock 2400 400 200 2.8 630

McArthur River Hard rock 2680 305 470 1.6 900

Ridgeway Trunk Hard rock 1213 226 1100 3.4 1050 ST2240

Gordonstone Drift Coal 1555 215 5000 5.0 1800 ST4500

Cadjebut Hard rock 2500 200 300 2.5 850

Revenge Hard rock 1500 185 450 1.6 1200

Long (overland)

Curragh North Coal 20 035 68 2500 7.5 1200 ST1500

Crinum Coal 9955 52 1100 4.9 900 ST1600

Dawson CV-193 Hard rock 16 300 4 2400 5.1 2 × 35 ϕ cable belt

Channar Hard rock 10 400 0 2200 4.1 1050 ST3150

KPC Coal 13 100 0 1350 5.3 1000 ST2250

Lafarge Surma Hard rock 17 000 -120 800 3.0 750 ST1800

TABLE 1Details for typical long (overland) and high lift troughed belt conveyors (Baigent, 2005; Kusel, 1999; McLennan, 2001).

0

200

400

600

800

1000

0 2 4 6 8 10 12 14

Length (km)

Lif

t(m

)

Ridgeway Portal

Increase Length, Reduce Lift

ST5500Increase Carcass Strength

(reduce troughability)

FIG 6 - Limits of length and lift based on the Ridgeway Portal configuration with 840 t/h, 3 m/s, splice FoS = 6.7 for ST500 to ST7100.

Loss of strength at the splice is presented here based on:

• no carcass splice (hence no loss of strength) for the upperdata points, and

• spliced carcass with loss of strength increasing by five percent with number of splice steps above two (DIN 221011982:02) for the lower data points.

Advances in splice design have reduced the magnitude of theloss of strength at the splice for the higher strength multi-stepsplices.

The weight of covers is based here on the standard minimumthickness (increases with increases in carcass strength, DIN 221011982:02) with an additional carry cover thickness of 6 mm.

The knee in the free length curves tends to favour designsbased on carcass constructions with strengths less than aroundST3000. Designers of long (overland) conveyors have exploitedthis characteristic. Table 1 shows that long (overland) conveyorsgenerally utilise lighter belt constructions. In the case of theCurragh North and Dawson conveyors, intermediate drives havebeen incorporated to reduce tensions, and hence to facilitate

lighter constructions. Splice factors of safety are reduced toaround 5.5 (Baigent, 2005).

Designers of high lift conveyors can exploit this characteristicin a similar manner.

The potential range of application of a new generation of highlift troughed belt conveyors is illustrated for the Ridgeway Portalapplication operating at 840 t/h, with belt speed increased from3 to 5 m/s and splice safety factor reduced from 6.7 to 5.5(Figure 8). This shows when comparing Figure 8 with Figure 6that the carcass could be reduced from ST5500 to ST2800, orthat the lift could be increased from 503 m to around 750 musing the existing ST5500 belt.

This illustrates the potential for utilising lighter belts for agiven application and hence reducing the capital and operatingcosts of the haulage system. Alternatively, this illustrates thepotential for applying a single flight conveyor to a greater lift andagain reducing the capital and operating costs of the haulagesystem by reducing the number of transfer/drive stations.

The key issues in achieving these increases in length and liftinclude:


INCLINED TROUGHED BELT CONVEYOR SYSTEMS FOR UNDERGROUND MASS MINING OPERATIONS

ST7100ST6300ST5500ST5000ST4000ST2800

ST2000

ST1000

ST500

0

1

2

3

4

5

6

7

8

9

10

0 1000 2000 3000 4000 5000 6000 7000 8000

Carcass Strength (kN)

Fre

eL

en

gth

(km

)

Reducing Troughability

FIG 7 - Free length for 1 m width of conveyor belt for no carcass splice (upper data points) and for spliced carcass (lower data points).

0

200

400

600

800

1000

0 2 4 6 8 10 12 14

Length (km)

Lif

t(m

)

Ridgeway Portal

ST2800

ST5500

FIG 8 - Limits of length and lift based on the Ridgeway Portal conveyor (840 t/h, with belt speed increased to 5 m/s and belt spliceFoS reduced to 5.5).

• Limit the additional strains applied to the belt by:

• designing chutes to minimise material impact at theloading point;

• selecting conservative pulley diameters, transitionlengths and vertical curves; and

• selecting drive and drive control equipment to limitdynamic effects when starting and stopping.

• Increase belt speeds/reduce belt tensions/reduce burden loadand address the resulting dust, life, noise, belt resonance andwear issues by:

• providing facilities to limit dust generation;

• selecting idlers, pulleys and drives for life and noiselimitation;

• installing idlers to avoid belt resonance; and

• designing chutes and/or accelerating belts to minimiseabrasion at the load point.

• Increase the fatigue life/load carrying capacity of belt splicesby addressing:

• splice design;

• temperature control, cleanliness and UV exposure whenforming the splice;

• splicing procedures and personnel training;

• quality of splice materials;

• quality of splicing equipment; and

• splice monitoring.

CONCLUSIONS

A number of technologies have contributed to the successfulapplication of troughed belts in underground mass miningoperations. These include:

• improved drive control equipment,

• belt condition monitoring,

• improved splice designs for higher strength and longer life,and

• improved chute designs.

Current designs are limited by a number of paradigms relatingto belt speed, splice factors of safety and the application ofintermediate drives.

The further exploitation of these technologies, focusing on anumber of key issues, will contribute to breaking down theseparadigms and facilitating the implementation of a newgeneration of high lift troughed belt conveyors.

REFERENCESAS1755 2000 conveyors. Safety requirements.Baigent, D, 2005. Curragh North materials handling project, in

Proceedings Bulk Materials Handling Conference, Mackay.DIN 22101 1982:02. Continuous mechanical handling equipment – Belt

conveyors for bulk materials – Bases for calculation and design.DIN 22101 2000:08. Continuous conveyors – Belt conveyors for loose

bulk materials – Basis for calculation and dimensioning.Kusel, B, 1999. The success story of self-extinguishing steel cord

conveyor belts in underground coal mining, International MiningQuarterly Review, 44.

McLennan, G, 2001. Energy efficient belt conveyor at BHP Gregory/Crinum, in Bulk Solids Handling, 21(1):73.

Nordell, L K, 1991. The Channar 20 km Overland – A flagship of modernbelt conveyor technology, Bulk Solids Handling, (11)4:781.

Pratt, A G L, 2005. Application of conveyors for underground haulage, inProceedings Ninth Underground Operators’ Conference, pp 273-283(The Australasian Institute of Mining and Metallurgy: Melbourne).

Pratt, A G L, 2008. Mine haulage – Options and the process of choice, inProceedings Tenth Underground Operators’ Conference, pp 179-188(The Australasian Institute of Mining and Metallurgy: Melbourne).

Troncoso, J, Francis, R and Pedersen, L, 1993. Design and constructionof coal handling facilities at Gordonstone Colliery, Bulk SolidsHandling, 13(4):823.



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