2009 IPCC Morrison and Lourel

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In-Pit Crushing and Conveying

D Morrison1 and I Lourel2

ABSTRACT

In evaluating the installation of an in-pit crushing and conveying (IPCC)system for any mine, a number of options are available for each of the digside, transport and dump side operations. Some of them are moreappropriate than others; given the pit arrangement, the material beinghandled and the rates at which it needs to be moved.

This paper seeks to document the options that might be employed, andto rank them in terms of their applicability at any mine and theirpracticality overall, with a view to nominating those that would be mostsuitable for further study.

SYSTEM DESIGN OBJECTIVES

For the purposes of this study, the IPCC and the associatedsubsystems are assumed to work under any of the followingconditions:

• continuous operation at 24 hours a day, seven days a week;

• maximise annual production hours; and

• the system will be owner operated and maintained.

EXISTING CONTINUOUS STRIPPINGAPPLICATIONS

There are a number of examples of continuous strippingoperations in other mining operations around the world and visitsto any or all of them would be appropriate during an assessmentof the technology.

Relocatable crusher options

The copper mining industry in North and South America has anumber of relocatable crushing systems. Escondida andChuquicamata mines in Chile, and the Bingham Canyon mine inUtah, USA, are among the largest mines in the world, eachemploying relocatable ore handling crushers (Figures 1 and 2)delivering onto large conveyors that reach to the process plantsvia long tunnels through the mine wall.

BHP-Billiton Mitsubishi Alliance, GoonyellaRiverside

The SHECON (Shovel conveyor) system at Goonyella was thefirst of the large mobile sizing rigs constructed (Figure 3).

The system was matched with a P&H 4100A, delivering

approximately 10 Mbcm/annum of overburden onto a conveyorsystem that is approximately 6 km long. The current limitationon the system throughput is thought to be a combination of conveyor capacity and operational methods. The shovel andcrusher are both capable of greater capacity than they arecurrently achieving.

The mobile sizing unit was supplied by MMD and began work in 2003. The conveyor system, onto which it delivers, was builtback in the early 1980s to form part of a bucket-wheel excavatoroperation.

Suncor Voyager, Canada

Currently there is a drive in the oilsands industry towards mobilemining systems. The oilsands industry is interested in thistechnology as a way to mobilise their ore mining and processingoperation. The current thinking is that overburden removal wouldstill remain a conventional, truck-and-shovel operation, while a

Iron Ore Conference Perth, WA, 27 - 29 July 2009 13

1. Manager, Integrated Mining, Sinclair Knight Merz (SKM), PO Box3848, South Brisbane Qld 4101. Email: [email protected]

2. Senior Applications Engineer, Sinclair Knight Merz (SKM), PO Box3848, South Brisbane Qld 4101. Email: [email protected]

FIG 1 - A 4500 t/h relocatable in-pit crushing station with a

gyratory crusher for copper ore at the ASARCO Inc Ray mine

in USA.

FIG 2 - Photograph showing a relocatable crushing station being

moved by a transport crawler.



mobile crushing and conveying system could be used to feed anin-pit slurry preparation plant.

Three major oilsands operators are already using mobilecrushing systems. Albian Sands has been using a semi-mobilecrushing plant (manufactured by ThyssenKrupp) since 2002.Syncrude has been conducting pilot tests since 2006 for an in-pit

slurrying system involving the use of a shovel-fed mobile crusherand conveyor system. Suncor Energy has been evaluating amobile crusher system (see Figure 4) on a commercial scale inpartnership with MMD mineral sizing. The pilot system, costing$150 million, was commissioned at 5500 tonnes of ore per hour.Suncor is considering additional mobile crusher units, with plansto employ mobile mining technology in their proposed VoyagerSouth mine.

Yimin open-pit coal mine, People’s Republic ofChina

ThyssenKrupp have supplied a system encompassing a fullymobile in-pit crusher, a crawler-mounted beltwagon, a hopperand cable reel car, a shiftable bench conveyor, a relocatableconveyor bridge (semi-mobile beltwagon), and a transport crawler.

Drummond, Colombia

Drummond Coal’s Pribbenow mine in Columbia has used adragline to load trucks via a ground hopper and an apron platefeeder (see Figure 5).

Anecdotally this operation has increased truck utilisation by15 per cent. There are also reports of good loading characteristics,resulting in reduced maintenance costs for the trucks.

There are thoughts of adopting the system to feed an out-of-pitstacking conveyor system, with the addition of a crusher/sizerbeneath the apron feeder.

The mine already uses the same style of feeder with a dozerfleet to load a sizer module (Figure 6), which in turn loads anoverland conveyor to take the overburden out of pit to a spreader.

SYSTEMS IN THE PIPELINE

Clermont

The Clermont Coal Mine Project open cut mining operation hasprocured a mobile IPCC system. When complete, the system willbe similar but not exactly the same as that installed at GoonyellaRiverside. The key difference will be the provision of abeltwagon allowing greater flexibility with regard to the bencheson which it will operate and the elimination of costly and timeconsuming moves of the face conveyor from bench to bench.

Clermont’s IPCC will be operated in conjunction with theshovel in two different extraction modes of operation. Early inthe mine life when pit room is at a premium, the system will beset up so that the mobile sizing rig’s feed hopper is placedbeneath a preformed concrete hopper. This will be used to

14 Perth, WA, 27 - 29 July 2009 Iron Ore Conference

D MORRISON and I LOUREL

FIG 3 - Goonyella Riverside SHECON operation.

FIG 4 - Mobile crusher unit being evaluated by Suncor Energy.

FIG 5 - Photographs showing dragline feeding trucks at

Drummond’s Pribbenow mine in Columbia.

FIG 6 - Dozer push-down operation at Drummond.



receive waste from truck haulage, allowing the truck fleet tomake short hauls and leaving the task of carrying the waste out tothe extremity of the ‘out of pit dump’ to the conveyor andspreader system (Figure 7).

Fortescue

Fortescue Metals Group (FMG) have engaged Rahco to providea continuous materials handling system for waste handling. Thesystem will include a pair of mobile feeder/sizer machinesloaded by hydraulic shovels.

OPERATIONAL MODELS

Methods of overburden handling

The basic processes involved in the handling of overburden can

be seen in Figure 8.

Any of the systems currently employed in the mining industrycan be characterised by one path or another through that flowchart. At one end of the scale most mines employ the simplestpath that passes through the top level. At the other end of thescale, Waihi mine in New Zealand employed the more complexpath of using all but the trucking directly to dump path,employing as they did, trucks to hoppers, to crushers toconveyors to trucks and then eventually to the dump.

Any combination is workable and all have their applications.

This block diagram could be represented as a flowsheet suchas that presented in Figures 9 and 10.

Each of the operations presented in that flow sheet can betreated separately. No single machine type selected at any stagedictates a specific path through this concept map.

Methods for combined overburden and orehandling

The basic processes involved in the handling of overburden couldbe expanded to encompass the movement of ore. This concept ispresented in Figure 10.

Seen on a more global basis, any mine could (eventually) becharacterised in accordance with Figure 10.

In this examination the excavation method, transport methodand dumping methods will be treated separately before focusingin on optimising the interaction of each one.

SYSTEM MOBILITY

Before considering which options might be worthy of furtherconsideration, it important to establish a common understandingof how the systems operate and then to label them in accordancewith the methods of operation.

Systems that might be considered as part of this study can havevarious degrees of mobility; there are three basic distinctions:

1. fixed structures,

2. relocatable structures, and

3. mobile structures.

Fixed structures

Fixed structures are those that are anchored to the ground and inwhich some degree of disassembly is required for relocation.Typically, the primary crushing stations already in place at anymine are of this type.

Relocatable (semi-mobile) structures

Structures that operate in one location for considerable periods of time and, can be readily moved (see Transporters section) whenrequired. For example, conveyor drive heads and tail stations (seeFigure 11) and track-shiftable conveyor modules (see Figure 12).

Mobile structures

Mobile structures are those that can relocate by themselves.Mobile structures can be carried on rail or they can be crawlermounted. Some smaller types of mobile equipment used in IPCCsystems are mounted on tyres that are can be retracted duringmachine operation.

Transporters

Relocatable structures can be moved from one location to anotherusing a transport crawler (see Figure 13) or use detachable walkersystems (see Figure 14).

EXCAVATION TECHNIQUES AND MACHINES

General

Selection of excavation machinery is fundamental to the successof any mining operation. The types of equipment that might beused at the mine face are presented here, and from that possiblefleet, a recommendation is made.

Excavation machines

Selection criteria for excavation machinery may include:

• ease and cost of electricity reticulation into the pit,

• mobility,

• throughput,

• capital cost,


IN-PIT CRUSHING AND CONVEYING

Excavation of

overburden

Trucking

Sizing Conveying

Overburden

dumps

Trucking

Drilling

and

blasting

FIG 8 - The basic overburden handling processes.

FIG 7 - The Clermont Spreader erection.



• productivity (cycle time per pass),

• materials handling characteristics, and

• face and bench operations.

Understanding the characteristic performance of the availableexcavation machines is necessary before establishing the capacityof the crusher and any out-loading conveyor system.

By way of example, to best utilise the excavation productivityof a machine, full utilisation of the suspended load rating while



FIG 9 - Process flow diagram showing multiple waste handling options.

Orestockpiles

Drillingand

blasting

Trucking

Excavation of

overburden or

ore

Trucking

SizingConveying

Overburdendumps

FIG 10 - The basic overburden and ore handling processes.

FIG 11 - Relocatable conveyor head and tail end stations.

FIG 12 - Track-shiftable conveyor modules on hollow steel skids.



excavating, and making short swings are both required. This hasan impact on the machine selection as well as the conveyorconfiguration.

Table 1 gives an overview on different types of excavationmachines used in opencast mining and their indicativeperformance envelopes.

The selection of optimal excavation machines will depend on anumber of drivers. Table 2 rates the available options against anumber of key parameters.

Dipper selection

For a typical truck and shovel operation, the shovel dipper issized to match the capacity of the trucks being loaded so that aunit number of passes fill the truck. For an IPCC installation, thegreatest total throughput is achieved when the entire system isable to cater for the whole operating cycle of the excavationmachine, and that is achieved when the crusher and conveyorsare able to clear the short-term peak loading rate from the shortswinging cycles, while minimising the need to relocate themachines. Therefore, the dipper should be sized in considerationof:

• weight of the protective wear package,

• weight of the dipper itself,

• density of the material being excavated,

• packing efficiency (presence of large voids) of the bulk material inside the dipper, and

• the average skill level of the operators.

In some instances, the use of separate dippers for different bulk materials may offer a significant improvement in productivity (upto 25 per cent) improvement by maximising the full loadingcapacity of the excavation machine.

SIZING

Before the overburden may be conveyed, it needs to be reducedto a top size of -450 mm by a primary sizer, in order to fit ontothe conveyor and to prevent physical damage to the conveyorcomponents during transport.

Short hauling trucks to in-pit hoppers/sizers/crushers and thenonto conveyors can be quite successful, and provided the dumpstation doesn’t have to be relocated frequently (say less oftenthan once every five years or so) they can be quite economic.This option needs to be considered further, particularly as itseems that each of the dump hoppers could remain in position forthe life of the pushback.

The use of mobile sizers delivering onto conveyors could also

be quite successful. The Goonyella/Riverside system operateswith quite a low typical operating cost although the system hasbeen poorly configured (being based on a ‘hand me down’conveying system used in a previous mining system) and requiresfrequent – and expensive – bench and face relocations. On theother hand Suncor have used a mobile conveyor system behind amobile sizer and this arrangement has been reasonably successful.

Interestingly, Clermont have begun construction of a mobilesizing unit which is intended to be used in conjunction with alarge rope shove, but during the early mine life, when pit room istoo tight for the fully mobile operation, the system will beinstalled beneath a truck dump hopper and then will be used tosize and convey material from short hauling trucks.

Crusher selection

Crusher configuration selection depends on:

• uniaxial compressive strength (UCS) of the material beingpresented,

• required throughput,

• power consumption and mechanical strength of machine,

• abrasiveness,

• max feed size, and

• wear component replacement cost and frequency.

Table 3 presents crusher options that are available for inclusionin a crushing rig and their key performance envelopes.

Any or all of those crusher types could be employed in a

mobile or relocatable sizing rig. The rolls sizer or breaker/ feeders would be the most appropriate for any mine recognisingthe capacity required and the material being mined.

A breaker/feeder could be successful at any mine, although thewear costs for chains and picks is likely to be high. There is notechnical reason why a breaker/feeder should be excluded fromconsideration at any mine, so the option of either a rolls sizer or abreaker/feeder unit needs to be considered further.

Semi-mobile sizing rig configuration

With one of the recommended options for further developmentbeing the use of trucks on short hauls to in pit dump stations, it isimportant to establish the optimum configuration of such amachine.

Two crushing/sizing options have already been touted assuitable:



FIG 14 - Detachable hydraulic walker for Goonyella’s relocatable

conveyor drive heads.

FIG 13 - A transport crawler shifting a conveyor drive head.





Machine type Capacity Notes Vendors

Dragline

Walking draglines

• Bucket 12 - 170 m3.• Boom 53 - 130 m.

• Can reach depth of 65 m inheight.

• Average operating life of 40years.

• The lowest removal cost per ton.• High capital cost.

• P&H (eg model 9160).• Bucyrus (eg model 8750).

Crawler draglines• Bucket 15 m3.• Boom 43 - 61 m.

Payload capacity

• 360 t.

Working weight• 7300 t.

Electric rope shovel

Payload capacity• 19 - 130 t.• Dipper 8 - 80 m3.

• A large shovel (eg the 104 tonneP&H4100XPB pictured) shouldbe capable of mining at10 000 t/h, or 50 Mt/a with and44 Mt/a without a belt wagon.

• A medium sized shovel (eg59 tonne P&H2800XPB) shouldbe capable of mining at 5000 t/h,or 30 Mt/a with and 24 Mt/awithout a belt wagon.

• P&H (eg model 4100XPB).• Bucyrus (eg 795 series).

Working weight• 1500 t.

Hydraulic excavator/shovel

• Bucket size 7 - 45 m3 (up to 90 t).• Operating weight 100 - 1000 t.• 477 - 3280 kW.

• Good mobility and versatility.• A large hydraulic excavator/

shovel (eg Terex O&K RH400pictured) now offers a comparablebucket size to that of the largestelectric rope shovel available.

• Terex O&K (up to 45 m3 bucket,Hitachi, Leibherr (model R996,up to 34 m3 bucket), Komatsu(model PC8000, up to 38/42 m3

bucket for a excavator/shovel).

Front end loader

•

Bucket size 12 - 40 m

3

(up to 70 t).• Operating weight 110 - 270 t.• 783 - 1715 kW.

•

High mobility and versatility.• A large front end loader (eg theLeTourneau L-2350 modelpictured) should be capable of mining at 2000 t/h.

•

LeTourneau, Komatsu,Caterpillar.

Dozer (crawler or wheeled)

• Up to 650 kW.• Blade capacity up to 45 m3.• Operating weight 110 t.

• High mobility and versatility.• Small capital investment.• Can be used to push material

directly onto an apron feederbelow.

• Komatsu (eg D475A-5EO),Caterpillar (eg 844H WheelDozer).

TABLE 1Excavation machines types.

Shovel

Excavator



1. rolls sizer, and

2. breaker feeder.

Mae Moh mine in Thailand uses a rolls sizer in a relocatabledump station structure. This arrangement is depicted in Figure 16.A similar system would be a suitable choice for any mine.Alternately consideration of something similar to the installationat Waihi Gold mine, which used a breaker/feeder in a fixed dump

station that discharged onto an overland conveyor system, wouldbe suitable for any mine. The equipment configurations aresimilar.

Mobile rig configuration

For high capacity operation, either a mobile rig carrying a rollssizer or alternately a breaker feeder is appropriate. Configured

for shovel dumping, the rigs are similar in conception. Both needto be considered in detail prior to determining the optimumequipment configuration. Some of the issues appropriate in theirconfiguration are discussed in the sections that follow.

Bench design and face operation

The selection of IPCC equipment will depend on:

• layout of pit,

• blasting and mining sequence,

• dump location and method,

• excavation equipment,

• number of active face and track shifting arrangement of track-shiftable conveyors, and

• degree of flexibility in mining operation required.



Bucket wheel excavator

• Bucket size.• 40 000 t/h.

• Goonyella used a bucket wheelexcavator (1980 Krupp modelL1367, 5200 m3 /hr)to removeupper benches of overburden.The deeper overburden isremoved by a dragline.

• FAM, Krupp, Voest-Alpine,Takraf.

Bucket ladder excavators

• 14 500 m3 /h.• Cutting at heights up to 40 m.• Excavation up to 32 m deep.

• Not reliable, being phased out. • FAM.

Continuous surface miner

• Peak cutting rate of 2800 bm3 /h.• Maximum cutting drum width

= 250 - 7400 mm.• Maximum cutting height

= 0 - 2.9 m.• Total installed power

450 - 3340 kW.• Working weight 40 - 540 t.

• Capable of mining material up to100 MPa without drilling andblasting.

• Precise cutting (minimumdilution) can be achieved.

• Can be used to load directly intotrucks.

• A belt wagon can be utilised totransfer mined material onto arelocatable face conveyor whichsits multiple benches away (bothhorizontally and vertically).

• Wirtgen, Bitelli, Huron (middledrum).

• Voest-Alpine (front cuttingboom).

• Krupp and Takraf (front cuttingdrum).

TABLE 1 Cont ...Excavation machines types.

Parameters

Mobility

Reliability

Volume per pass

Capital cost

Operating cost

Compatibility

Flexibility

Accuracy/operator skill independence

TABLE 2Performance matrix of various excavation machines.





Crusher type Capacity (t/h) Max feed size (mm) Weight (tonnes)

Gyratory crusher

Vendors: FL Smith, Metso Minerals,Kawasaki, etc.

1000 - 10 000 1000 - 1600 180 - 750

Jaw crusher

Vendors: ThyssenKrupp, Nordberg,Metso Minerals, etc.

55 - 120010 - 165

Hammer crusher

Around 2000 t/h Extremely large reduction ration canbe achieved.

Crusher type Capacity (t/h) Max feed size (mm)

Rolls sizers

Vendors: ThyssenKrupp, MMD,Abon, etc.

Up to 15 000 Up to 2000 10 - 250

TABLE 3Available options for crushers/sizers.



Where blasting is required, the bench arrangement needs toprovide physical separation between blast zone and location of any face conveyors (a separation of more than 30 m is typicallyrequired to provide some fly rock protection).

Generally speaking, mining a wide face while tramming theshovel in a circular pattern around the crusher hopper, offers thebest overall productivity. For a large shovel, a 60 m pass widthoffers the greatest productivity. In that arrangement, the maximumswing angle that the shovel is required to use is 110°, and themedian swing is 83°. Configuration of the sizer rig needs toconsider this operating method, particularly the selection of theboom length.

Sizer feed

Typically, a heavy-duty apron feeder is used to feed the primarycrusher in a mobile sizing rig. This is the key difference betweena rig using a sizer and one using a breaker/feeder. The breakerfeeder uses a chain feeder that runs beneath a pick breaker.

Chain wear is a serious consideration with breaker/feeders andwhile this style of rig may have a capital cost advantage, their



Crusher type Capacity (t/h) Max feed size (mm)

Breaker feeder

Vendors: Abon, McLanahan, etc.

Up to 6000 Up to 10 000

TABLE 3 Cont ...Available options for crushers/sizers.

Fixed sizing

station

Fully

mobile

sizing rig

A fully mobile sizing rig is a self-contained unit with its

own moving gear.

Each crushing plant comes ready to operate with its own

feed hopper, feed conveyor, discharge conveyor and

material transfer belt (refer Figure ).

Throughput limited by the size of the onboard equipment,

which are selected based on practical weight/height for a

mobile structure.

For softer materials (UCS < 175 MPa), the existing rolls

crusher technology can yield a throughput of around

10,000tph.

For harder materials, where rolls crushers become

unsuitable, throughput is generally limited to 5,000tph.

Sizing rig is built into a permanent pit face. Throughput is

only limited by the largest sizer/feeder available.

Relocatable

(semi-

mobile)

sizing

station

Relocatable or semi-mobile sizing stations have no movinggear of their own. A varying amount of effort is required to

disassemble the unit for transportation as piggyback load(s).

• Semi-mobile sizing stations are appropriate when a change

of location is infrequently required.

Can significantly lower in-pit transport costs.

•

•

•

•

•

•

•

•

FIG 15 - Fixed, relocatable and mobile sizing station

configurations.

FIG 16 - Relocatable sizing rig installed at Mae Moh mine inThailand.

FIG 17 - Fully mobile sizer unit in operation at Goonyella mine.

FIG 18 - Mobile breaker/feeder unit (in this instance configured to it

can be fed by dozers, but could have a walled hopper fitted over

the feeder).



operational performance can be compromised by highermaintenance costs.

TRANSPORT OPTIONS

General

Options for material transport could be characterised by:

• conventional truck/shovel operations;

• truck/shovel operations delivering into relocatable hoppers,from which the waste/coal/ore is conveyed away;

• shovel to sizer operations which deliver to conveyors;

• shovel to sizer operations which deliver to conveyors andthen feed into trucks to allow selective dumping at the dumpsite; and

• truck/shovel to hopper applications delivering to conveyorsthen to truck loading stations for selective dumping.

The two latter options (selective dumping) are particularlyattractive options where run off acid or alkali leaching, salinity, orwaste dump stability issues are important, allowing as they do theoption of low cost haulage combined with placing material inspecific locations after it is delivered near to the site. Waihi minein New Zealand has been employing this technique for a numberof years for the construction of their tailings impoundmentstructures.

Shovels loading trucks is a system with great operational

flexibility and little operational risk. On the other hand, its

operating cost profile is subject to labour cost variations, liquidfuel prices and periodic equipment replacement. The low risk profile of this option means it deserves to be the base case for theprefeasibility study, but other – less flexible – options coulddrastically reduced the cost of overburden removal.

In deciding what alternate transport option works best for anymine, it is important to establish what is practical, and also what

is already in use elsewhere in the industry, for a number of



Machine type Capacity Vendors

Up 20 000 t/h Numerous

Up to 15 000 t/h Numerous

TABLE 4Dump machine types.

Tripper

Spreader Capacity Vendors

Up 20 000 t/h Various

TABLE 5Dump machine types.

FIG 19 - Feed hopper and apron feeder onboard Goonyella’s

mobile in-pit crushing station.



reasons. Any existing system will have been a compromise inone way or another and there will be a number of lessons to belearnt from examining that system. Being the first to employ aform of technology carries some degree of risk and acontingency would need to be budgeted and drawn down toimprove the performance of the system if any of the compromisesin either cost, performance, materials or equipment proved to beincorrectly founded.

Relocatable conveyor systems

Options worth considering in an IPCC system include conveyorsthat run overland, comprising a number of discrete units, andalso a number of options for self-contained mobile conveyorsystems that allow greater flexibility in mine operations, transportand dumping (admittedly with a corresponding increase incapital and operating costs).

The trunk or overland conveyors comprise four majorcomponents, these are:

1. relocatable drive head assembly,

2. intermediate modules that carry the belt,

3. relocatable or pivoting tail end assemblies (with or without

drives attached), and

4. mobile hoppers for loading the conveyor.

Head end stations

Shuttle conveyor head end

In the instance when more than one destination has to beselected, or when trucks are being loaded from a conveyor, ashuttle head arrangement may be considered. The configurationdepicted in Figure 20 and Figure 21 was employed at Waihi Goldmine.

A similar arrangement would be used to transfer to more thanone conveyor.

Tail end station

Because the conveyors will typically be relocatable, tail stationsthat are not fixed to concrete foundations are required. The bestsolution to the need to anchor the tail end in place is the use of bored holes with steel pickets and restraining chains. This

arrangement is depicted in Figure 23.

Dump conveyors typically operate on a pivot arrangement(because it is easier to move the conveyor beneath the spreader if it is only moving at one end). That usually involves a large piledconcrete structure beneath the tail end to anchor it into position.

Mobile conveyors

Fully mobile bridge conveyors can be used along the movingmine face, across a pit, between mined benches, or for dumpdevelopment.

This option greatly reduces the production time lost throughface relocations and face movements. The most appropriateconfigurations for any mine are presented in Figures 24, 25, 26and 27. Effectively these are mobile machines of the same type asthe sizing rig, upon which has been installed a single long beltconveyor. At present the longest unit in service is approximately1500 m. The machine comprises a number of gantries, eachsupported by a crawler mechanism. The drives are coordinatedby a Global Positioning System (GPS) based system to ensurethe horizontal alignment of the conveyor. Joining each of thegantries are pin joints that allow a degree of verticalmisalignment, so the system can operate along slightlyundulating benches. This is the style of conveyor installed behindthe mobile sizer at Suncor’s Voyager mine.



FIG

20 - Photograph of a relocatable drive head assembly.

FIG 21 - Arrangement of a shuttle conveyor head end showing

shuttle in the fully retracted position.

FIG 22 - Arrangement of a shuttle conveyor head end showingshuttle in the fully extended position.

FIG 23 - Photograph of a typical relocatable tail station secured by

chains and ground anchors.



Conveyors of this type would be an appropriate for faceoperations with a fully mobile sizing rig, removing as they do theneed to shut the system down for extended periods while theconveyor is relocated.

Correctly configured machines of this type are able to traversequite steep grades (of the order of 20 per cent) and couldtherefore move from bench to bench by walking down a graded

slope. The preparation would only be necessary ahead of thecrawler mechanisms (situated at 40 m intervals) rather than alongthe full length of the machine.

Belt wagon

A belt wagon can serve as a link between a mobile sizer and aface conveyor. It allows operation of a mobile sizer at bencheseither above or below the horizon where a relocatable, in-pitconveyor is mounted. Alternatively, a belt wagon can be used toextend the operating range of the excavation and crushingoperation (increasing working distance from a face conveyor). Atypical belt wagon is a fully mobile structure (crawler mounted)supporting a receiving and a discharge conveyor which can slewand luff independently.

With any mine likely to operate typically over many benches,means of conveying from one bench to another are going to bevitally important is costly and time-consuming dismantling andreconstruction of face conveyors is to be avoided.

The use of a belt wagon should be considered in any fullymobile operation because of the increased flexibility it offers.

Bridge conveyors

An option that should result in fewer trunk belt relocations is toconsider the use of a bridge conveyor. These units serve a similarpurpose to a beltwagon, although they are typically longer andsupported at both ends.

Piggy-back conveyor

Piggy-back conveyors are short-centred conveyors which cangreatly enhance the degree of flexibility of an IPCC. There may

be situations in the configuration of an IPCC system where theuse of such a conveyor (or several) might be appropriate.

Ulan mine operated a fleet of 20 of these conveyors behind amobile crushing plant for many years. The system is depicted inFigure 29.

Hopper and cable reel car

Hopper cars and cable reel cars are necessary for transferring thematerial onto a conveyor and supplying power to the mobileequipment (Figure 30).

In developing the face operation, any or all of these optionscould be considered and decisions on the use or not of eachsystem will be dictated by the method of operation that gives thegreatest up time combined with the best capital cost.



FIG 24 - A pivoting tail station arrangement for radial trackshifting a

dump conveyor.

FIG 25 - Photographs of bridge-style conveyors supported by

multiple crawlers. These conveyors can be used on mine face or atthe dump (operable at a maximum slope of 2°).

FIG 26 - Photographs of a belt wagon.

FIG 27 - Photograph of a cross-bench bridge conveyor.



DUMPING OPERATIONS

A number of options exist for placing material on the dump. Twofunctions are required, a means of getting the material off thebelt at any location along the length of the belt and a means of

placing the material where it needs to be placed. Trippers servethe first function. After the tripper a travelling stacker or spreaderthat can be used to place the material in the appropriate manner.

Two different styles of dump conveyor could be considered.The most common is the trackshifting arrangement where dozersare used to relocate the conveyor, by sliding the conveyorsideways on skids. The other option is to mount the dumpconveyor on mobile gantries, which are self propelled.

The advantage of the self propelled gantries is the ability tocombine the tripper unit and the spreader discharge boom intothe same piece of equipment, so while the conveyor itself ismuch more expensive than a trackshifting unit, the extra cost is

offset by the reduction in the cost of the spreader.Dumps are typically very large and crawler mounted dump

conveyor of the length required to reach all the way across thedump have not yet been built.

Under the circumstances the most appropriate dumparrangement is to use a crawler mounted spreader, fed by acrawler mounted tripper which is integral with a track shiftingconveyor. Mounting both the tripper and the spreader on crawlersallows for lower ground bearing pressures and easier conveyormoves. Alternately the use of crawler mounted conveyors withintegral tripper could be considered, although the geotechnicalissues related to their close proximity to the edge of the dumpwould have to be considered in detail before a decision to goforward with one of these machines.



FIG 29 - IPCC operation at Ulan utilising up to 20 piggy-back

conveyors in series.

FIG 30 - Photograph of an existing mobile feed hopper

arrangement.

FIG 28 - Schematic of a mobile crushing system feeding multiple piggy-back conveyors.

FIG 31 - Photograph of a feed hopper arrangement.

2009 IPCC Morrison and Lourel

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Transcript of 2009 IPCC Morrison and Lourel