integrated design of an xlp dozer · underground mining imposes very rigid constraints on mobile...

INTEGRATED DESIGN OF AN XLP DOZER 263

IntroductionFor several years mechanization has had a tremendousimpact on the underground mining industry. Successfuldevelopment of new mechanized mining systems requireslong-term collaborative partnerships between many parties,including mining companies, equipment suppliers andacademic institutions [Robbins (2000)]. As a specific case,underground narrow-reef platinum mining in South Africahas driven innovation in increasingly sophisticated miningmethods with advanced machinery. The aim of suchinnovation in mechanization has been primarily concernedwith increasing productivity and improving safety. Ageneral discussion of the issues regarding the introductionof mechanization in an underground narrow reef mine ispresented in Willis et al. (2004). Among the criteriaidentified for successful introduction of mechanization, anoverall ‘holistic’ integrated approach is deemed essential.This includes concurrent consideration of mine design andequipment selection. Thus, the design and development of anew machine (or suite of machines) simultaneously with thedevelopment of a new mining method has the potential toachieve significant symbiotic benefits.

Mechanized mining methods utilizing specialized extralow profile (XLP) machines for narrow-seam platinummining are currently in various stages of development inSouth Africa. A comparison of traditional mining methodswith XLP mechanized mining of UG2 in the BushveldComplex shows that XLP mining had the lowest wastedilution, highest production rates, lowest overall costs andthe best head grade [Egerton (2004)]. A detailed account ofXLP mechanized breast mining at Anglo Platinum can befound in Harrison (2006). The results of trials from variousmine layouts in different locations are described. When

benchmarked against conventional mining and low profileroom and pillar methods, it was shown that XLPmechanized breast mining has the ‘potential to add morevalue’. Another account of the development andimplementation of mechanized breast mining by acollaboration between Lonmin Platinum and Sandvik ispresented in Pickering and Moxham (2007). Details areprovided of the development process of the XLP suite oftrackless mining equipment consisting of a drill-rig, roofbolter and loader.

The focus of this paper is to discuss the development ofone particular machine, the Sandvik LZ100L dozer,designed to perform a specialized task within the overallmining method of XLP mechanized breast mining in SouthAfrica. This will include a description of the machine andits function with respect to its operating environment andthe overall mining method. Also, certain aspects of thedesign process will be highlighted along with specificdesign issues. Finally, some other novel applications will bediscussed for which the machine is well suited outside of itsintended design function.

The LZ100L dozer—an overviewThe Sandvik LZ100L dozer, shown in Figure 1, is an extralow profile (XLP), remote-controlled undergroundbulldozer designed to operate in low-back (ceiling) workareas. With its compact body design, crawler tracks, andhydrostatic drive system, the machine is highlymaneuverable and responsive, allowing users to quickly andsafely move material throughout the mine.

The base machine dimensions are 850 mm (h) � 1 600mm (w) � 2 750 mm (l) and the weight is 5 700 kg. It ispowered by a four cylinder, indirect injection diesel engine

OLSEN, S.G., HALL, R.A., DANESHMEND, L.K. and MURPHY, P.F.R. Integrated design of an XLP dozer. Third International Platinum Conference‘Platinum in Transformation’, The Southern African Institute of Mining and Metallurgy, 2008.

Integrated design of an XLP dozer

S.G. OLSEN*, R.A. HALL*, L.K. DANESHMEND† and P.F.R. MURPHY‡

*University of British Columbia†Queen’s University

‡Sandvik Mining & Construction

Underground mining imposes very rigid constraints on mobile equipment design. The choice of aparticular mining ‘method’—i.e. the specific mix of techniques for excavation, ground support,and materials handling—is greatly influenced by the nature of the orebody being exploited.Mining methods tend to be fairly conservative, relying upon well-established and provenequipment designs. In order to improve worker safety and productivity, South African platinummines have increasingly turned to mechanization. An added benefit of these mechanization effortsis that the nature of the mining can be modified based on the feasible equipment designs. Theseefforts have resulted in changes to the mining methods employed in South Africa’s narrow-reefplatinum group metal (PGM) orebodies, as well as the development of a suite of mobileequipment which enables implementation of the new production processes. This paper focuses onthe design and development of one of these machines—a narrow-reef bulldozer suited to selectivemining. The resulting machine is a miniature unmanned bulldozer and multipurpose crawlerplatform designed for narrow-vein mining applications, with integrated mechatronics and remotecontrol capabilities. This paper will discuss the development of the machine and the applicationsfor which it was designed.

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with turbocharger. An on-board electric fill pump andfiltration system is used for replenishing hydraulic oil. Eachcrawler track is driven by a variable hydraulic motor andthe blade is driven by two hydraulic cylinders. Among thesafety features is a fire suppression system with manualactuators located at two locations on the machine frame.

The drive configuration consists of an open-loophydrostatic circuit comprised of a single variabledisplacement pump, flow dividing valve, and two variabledisplacement hydraulic motors integrated with double-reduction track drives. The machine steers by stalling thetrack on one side while driving the opposing track. Bladefunction is limited to blade lift and lower on the standardmachine.

The LZ100L dozer was designed exclusively for remoteradio control operation with a hand-held controller. A900 MHz CAN-bus radio transceiver was custom-designedfor the machine in collaboration with a well-known supplierof underground mobile equipment radios. The radiotransmitter is slightly larger than a modern video gamecontroller, as shown in Figure 2.

The controller has several built-in safety features thatinclude dead man buttons on the upper edge of thecontroller that halts machine movement if the buttons arereleased, a tilt sensor that halts machine movement if thecontroller is tilted past a certain angle, a display screen tosend prompts to the operator, an emergency stop button,and a built in access code. Through an onboard embeddedCAN control, the LZ100L dozer is instrumented to gatherdata from sensors and send control signals to the actuators.

System monitoring and diagnostic capabilities areimplemented through onboard instrumentation, such aspressure transducers, temperature transducers andelectronic fluid level gauges, and allow the machine torespond quickly to events such as overheating, blockedfilters or an overloaded pump. An effective troubleshootingtool was developed to identify the type and location of aproblem and in some cases, provide a possible solution toassist operators and service personnel.

Development processSandvik Mining and Construction follows a well-definedOffering Development Process (ODP). The five phases ofthe ODP are: (1) collecting and screening, (2) business pre-study, (3) product development, (4) piloting, and (5)lifecycle management. In the discussion that follows, thefocus is on phase (3) product development in the context of

the LZ100L dozer. The product development phase of the LZ100L dozer

project began with the creation of a User RequirementsSpecification (URS) document in May 2004. The URS is ahigh-level document that does not detail specific features ofa machine itself, but rather the functional requirements andoperating conditions necessary for the system to accomplishits tasks without a predetermined solution in mind. The endgoal of the URS was the development of a specification fora panel-cleaning machine or machines for use in an XLPmining capacity such that the machines meet the functional,maintainability, serviceability, cost and schedulerequirements of the end user.

The next step in the process was to develop animplementation plan for the project. The objective of thispart of the process was to build the project team, establishthe project timeline, milestones and deliverables, and costtargets.

The initial concept design of the LZ100L dozercommenced in the second quarter of 2004. After just over ayear, a fully operational prototype entered service atLonmin’s Karee 1B mine in the third quarter of 2005. Aseries of extensive field trials were performed, followed bydesign improvements over the next eight months.Approximately 30 design improvements were made duringthis period. The following areas were identified forimprovement:

• Track assembly mounting• Track shoe configuration• Hydraulic oil cooling• Vehicle ground clearance• Engine control • Blade design.

Upon completion of design improvements, the LZ100Ldozer entered service at Karee 1B in the first quarter of2006, with full production beginning in the third quarter of2006.

Target applicationThe LZ100L dozer was designed to be used as part of anextra-low profile mining operation. The first step in theoverall ore extraction process is blasting of the face withexplosives. The blast is designed to throw as much materialas possible into the gully area. The resulting blasted

Figure 1. Sandvik LZ100L dozer Figure 2. Radio remote control

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material that fills the panel is a coarse mix of ore and wasterock with an uneven distribution of sizes and shapes.Approximately 40% of material blasted from the face isthrown into the gully. A bulldozer then removes theexcavation material from the very restricted space of thepanel to the gully. The gully is a larger, more open spacewhere an LHD (load haul dump) vehicle collects thematerial for transport to a conveyor hopper. This process isillustrated in Figure 3. The panel dimensions typicallymeasure 4 metres wide, 21 metres along the face and aslittle as 1 metre high from the floor to the roof.

The use of a radio-controlled bulldozer to accomplish thepanel clearance operation is a relatively new technique. Thestandard method to clear that panel is with large cablemounted buckets that are assembled and fixed to the walls

within the panel. These buckets are operated tocontinuously drag the excavation material into the gully.This is very dangerous due to the likelihood of cablessnapping. It is also very time-consuming to set up andreconfigure the infrastructure for the cable system.Moreover, the operator must be located further away fromthe panel. Therefore, the clearance operation cannot bemonitored as closely, so much of the excavation material isleft behind to be cleaned up manually.

On a historical note, early attempts have been made atintroducing miniature ‘remote’ bulldozers for materialremoval tasks in underground mining. One such machinedesigned in the 1960s is described in Anon (1962) asweighing 1 746 kg and having dimensions of 0.75 m high,1.5 m long and 1 m wide. The crawler track motors and

Figure 4. XLP mechanized ‘breast’ mining

Figure 3. Bulldozer panel clearance operation



blade positioning cylinder are actuated pneumaticallythough a handheld control box. The purpose of thismachine is to move broken ore into the paths of scrapers.

The overall extra-low profile mechanized breast miningmethod in which the panel clearance task is performed, isshown schematically in Figure 4.

The orebody (or reef) is typically only 1.1 metres high, sobreast mining is used to minimize dilution of the ore. Thefirst step in this method is to develop the gully. The miningcycle of drilling with an XLP drill rig, blasting, bulldozingand roof support with an XLP bolter then ensues. Groundconditions are generally quite good so no pillars arerequired along the face. It is generally sufficient to screenand bolt the back, with grout packs installed as required.

Design challengesThe harsh underground mining environment and restrictedoperating space presented a number of unique designchallenges. The major design issues are as follows:

• Traction: The steel tracks operating on friable bedrockexperience reduced traction and are subject to highabrasion.

• Cooling: The confined nature of XLP mining can makeventilation challenging.

• Impact damage: The frame is prone to frequentcollisions with the roof due to 1.1 m stoping width.

• Vibration: Steel tracks on bedrock lead to vibrationtransmitted through machine structure, affectingelectrical and hydraulic connections.

• Serviceability: The physical dimensions of the vehicleconstrain component layout and accessibility.

As mentioned previously, the design of the machinecommenced in Q2 2004. Approximately six weeks werespent evaluating sketches, CAD proposals and systemspecifications (hydraulics and electrical) prior to thecommencement of detailed design. Important designconstraints (apart from cost) were: machine dimensions(particularly the height), ambient operating temperature,power-to-weight ratio, traction and gradeability. Themachine layout was largely determined by dimensionalconstraints, together with the necessity to have the radiatorat the rear of the machine, so as to find room for the largeradiator fan shroud. A preliminary layout of major machinecomponents at week six is shown in Figure 5.

The blade linkage arrangement dictated the front of thechassis. A straight blade was chosen for the followingreasons: 1) Simplicity; 2) Higher kW/m3 and kW/m ratiosthan a U-blade; 3) Low cost; 4) Higher production than anangle blade.

Using an industry-accepted drivetrain sizing and selectionprocedure, computations were made in order to size thediesel engine, hydrostatic drive pump and motors. Theresults were then checked empirically against other dozerson the market. For example, the power-to-weight ratio isapproximately 8.2 kW/ton. This is in the middle range for aselected number of popular dozers used in the constructionindustry. A regression of engine flywheel power on weightfor this sample of dozers yielded a predicted requiredengine power of 46.6 kW, slightly more than the 44.7 kWengine selected for the machine. However, it is also knownthat the highest power consumption on a tracked vehicle iswhen the machine is turning. Construction dozers must turnin all types of conditions such as clayey loam, which hasvery high cohesion. In contrast, the LZ100L dozer operateson dry, sandy material, bedrock and the occasional pile of

small boulders. These conditions, combined with the factthat machine has comparatively high pushing power percubic metre of blade volume, and per metre length of blade,indicated that the engine selected was suitable for the job.

The crawler tracks were custom designed for theapplication. Although there are many readily availabledozer crawler tracks assemblies available for purchase fromaftermarket suppliers, none of the ones examined that wassuitable for the rugged application underground, were smallenough to fit on the machine. Thus, a crawler assemblydesign project was initiated with the supplier.

As with all other underground equipment design criteria,reliability and serviceability of components were bothextremely important. However, in the development of theLZ100L dozer, these considerations warranted increasedattention. This is because the project not only entaileddevelopment of a machine, but was part of a much largerproject, the development of an entirely new mining method,in which operating conditions are severe, and skilledservice technicians are scarce. Design features such asautomatic fire suppression, an on-board electric fillingpump for the hydraulic tank, and a radiator with self-cleaning features were purpose-designed for theapplication.

Field trial supportProper field trial support is critical to overall productdevelopment, as illustrated in Figure 6. Throughout theLZ100L dozer field trials, feedback was transmitted back tothe factory by onsite South Africa personnel, visits byfactory personnel and a MAXIMO database. MAXIMO is amaintenance management information system that has beendeployed to gather component reliability information aswell as machine performance information. It documentskey events with the machine such as repairs done to themachine, time the problem occurred, and the totaldowntime resulting from it.

Design reviews were conducted frequently throughout the12-month trial, based on field trial feedback. Some aspectsof the prototype design were improved and implemented asthe trial progressed, such as blade design, crawler trackshoes and radio control. This process was repeated until thetargeted KPIs (e.g. reliability, availability and operatingcost) were achieved, signaling an end to the trial.

Figure 5. Preliminary layout of major components at week six



Design improvements were made to certain aspects of thevehicle as more detailed knowledge about the operatingconditions was gained. Some specific design improvementsare as follows:

• The size of electrical panel was increased and mountedon sliders to facilitate connector access andserviceability

• The fan shroud was mounted at the rear of the machineto facilitate wheel motor fitting access.

• The top covers and support structure were redesignedfor easier removal to facilitate access to internalmechanical components.

• Extreme-abrasion hydraulic hoses were introduced toreduce hose jacket chafing due to the vibration of themachine

• Wear components were incorporated into blade toextend blade life.

Future developments—leveraging the designto other applications

In addition to XLP mining, there is excellent potential forthe LZ100L dozer in other mining and constructionapplications. One particular application was demonstratedat an opencast tar sands mine in Western Canada. TheLZ100L dozer was shown to be able to effectively cleanpiles of tar sand accumulated under ore preparation plantfeed conveyors. This is currently accomplished with front-end loaders. The benefits of using the LZ100L dozer forthis task are as follows:

• The machine operator may be located at a safe distanceaway from the dangerous area directly beneath the oreconveyors.

• The machine operator may sit comfortably in the cab ofa pickup truck, rather than being exposed totemperatures lower than -40°C that are possiblethroughout the winter.

• The machine itself is capable of moving more material,more quickly than current means due to greater powerand traction.

• Since the machine has such a low profile, feedconveyors may be built lower to the ground, thusreducing infrastructure cost.

Furthermore, the LZ100L dozer has tremendous potentialfor research and development of robotics applications. Acollaborative project is currently underway with theUniversity of British Columbia, Queen’s University andSandvik Mining and Construction to investigate anautomated XLP panel clearance system. The onboardmobile computer control system, along with variousonboard sensors such as pressure transducers and trackspeed sensors are well suited for developing andimplementing innovative capabilities. Ongoing research isfocused on the development of traction control to reducetrack shoe wear, modelling of machine-terrain interaction,control algorithms incorporating the coupled effects of theactuators and autonomous task execution.

ConclusionsAn extra low profile remote operated bulldozer has beendeveloped and is currently being employed in mechanizedplatinum reef mining operations in South Africa. Thismachine, as a component of an XLP suite of machinery, hasmade a valuable contribution to an innovative newapproach to mechanized platinum mining. Unique designchallenges were overcome and new applications werediscovered to make use of the capabilities of the LZ100LDozer.

References

Anon. Bulldozing in low headroom stopes’ Mining Journal,vol. 258, no. 6598, February 1962, p. 113.

ROBBINS, R.J. ‘Mechanization of underground mining: aquick look backward and forward’ InternationalJournal of Rock Mechanics and Mining Sciences, vol.37, no. 1–2, January 2000, pp 413–421.

EGERTON, F.M.G. Presidential Address: Themechanization of UG2 mining in the BushveldComplex, Journal of the South African Institute ofMining and Metallurgy, September 2004, pp.439–448.

Figure 6. Field trial support with the design cycle



WILLIS, R.P.H., DIXON, J.R., COX, J.A. and POOLEY,A.D. A framework for the introduction of mechanizedmining International Platinum Conference ‘PlatinumAdding Value’, Sun City, South Africa, October2004, pp. 117–124.

HARRISON, G.A. Implementation of extra low profile(XLP) mechanized equipment in Anglo Platinum

Journal of the South African Institute of Mining andMetallurgy, vol. 106, August 2006, pp. 527–532.

PICKERING, R.G.B. and MOXHAM, K. The developmentand implementation of the Lonmin mechanized breastmining, Journal of the South African Institute ofMining and Metallurgy, vol. 107, January 2007, pp.5–14.

Scott Graham Olsen

University of British Columbia

Currently a doctoral candidate in Mechanical Engineering at the University of British Columbia, specializingin Robotics. Research pursuits are focused on automation of mobile mining equipment.


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