Crocodile River Mine’s Long Haul to Sustainable Production
High platinum prices do not necessarily make South Africa’s deposits easy to mine profitably and safely. A well-planned ore transportation system can help
By Kyran Casteel, European Editor


Truck haulage to the conveyor has helped improve operating costs at De Beers’ Crocodile River mine.
In the South African diamond industry De Beers has achieved highly mechanized underground mining, including world class automation of the haulage system at Finsch, as discussed in the January- February E&MJ cover story, and commenced remote controlled LHD operation at Cullinan. But platinum group metals (PGMs), mining companies exploiting the limited height reef deposits of South Africa’s Bushveld Complex find that just basic mechanization still presents some difficulties and high metal prices do not guarantee profitability. The Crocodile River mine (CRM) is one operation that has had to confront this challenge.

Although both the reef deposits hosting Bushveld PGM mineralization and those which are chromite rich are often easy to access by drifts and sufficiently continuous down dip to be mined by room-and-pillar or breasting methods, the seams are typically only 0.6–1.5 m thick. This effectively precluded mechanized production drilling until Boart Longyear, Sandvik, Atlas Copco and others were able to build low-profile equipment starting around 2000. Similarly, only the low-profile load-haul-dump machines developed by GHH Fahrzeuge, Sandvik and Atlas Copco can load blasted material directly from the face. However, standard LHDs have been quite widely utilized since the 1990s in lateral roadways to collect ore from ore passes. They either load it onto conveyors for delivery to surface or, where the distance is short enough, they may proceed up ramp to the surface.

Several mines, including Crocodile River, consequently employ a hybrid mining system. Excavation combines manual drilling with pneumatic jack leg drills, removing ore from the face to side and then main gulleys with scraper blade units drawn by winch-driven rope, and pulling the collected ore to an ore pass, again using a winch. Typically, LHDs collect the ore dropped to the haulage level and carry it to the conveyor loading system for transport to surface. The tons per hour productivity of these and even the more mechanized systems is limited to some extent by the transport logistics and/or the capacity of the low profile machines. So CRM is using truck haulage to boost output rates.

Confounding the Doomsayers
The Crocodile River operation, located at the eastern end of the Western Limb of the Bushveld Complex, dates from 1987 and was originally designed to be a fully mechanized mine. However, things did not go according to plan and, during particularly difficult PGM market conditions, mining problems were sufficiently difficult to force closure in both 1991 and 2003. Productive life at CRM restarted with dewatering of the underground mining areas in 2005 after the Platinum Consortium took control of the owner, Barplats Investments Ltd (BPIL). During 2006-2007, the Canadian firm Eastern Platinum (Eastplats) built up a controlling interest in BPIL which also owns other PGM assets. The remaining stake is held by a Black Economic Empowerment entity, The Gubavu Consortium, and the whole operation is now being planned on a 15-year life basis. However, some South African platinum industry analysts forecast in 2006 that Eastern Platinum would also have to close CRM by the end of 2007 because it would prove uneconomic to mine.



This conveyor (upper photo) presently brings mined ore up the No. 3 decline shaft to CRM’s process plant.
Meanwhile Murray & Roberts Cementation is refurbishing and deepening the vertical shaft, which will be able to
hoist 120,000mt/month.
According to Mine Manager Albert Hartmann, who came to the operation with 17 years’ experience in mining and three years of contracting, the belief that CRM is not viable is a myth. While he accepted there are mining problems, mainly created by finger faulting and the undulating nature of the reef, Hartmann was sure that economic mining was possible and set out to prove the closure prediction wrong, not only as of December 2007 but well into the future too. Increasing ore production at the existing mine sections to a sustainable level would provide the basis for new mine section development and other projects that can increase total CRM output to 240,000 oz/y by the end of 2009. Projects involving other properties—Mareesburg, Spitzkop and Kennedy’s Vale on the Eastern Limb of the Bushveld Comple— may then enable Eastplats to increase its total South African annual PGM production to 600,000 oz or more.

The Crocodile River mine exploits a property with its southern edge on the outcrop of the UG2 Reef, which here contains PGM values but also some chromite. This southern mineable part of the property is divided by significant faults into four sections. Two of these sections are presently worked: the Maroelabult section, subdivided into Maroelabult, which is mined, and Maroelabult North, lies on the eastern side closest to Brits; and the larger central Zandfontein section where CRM’s main surface facilities, including the workshops, concentrator and mothballed smelter, are located. The downwardly faulted Kareespruit section lies between Maroelabult and Zandfontain and the Crocette section is immediately west of Zandfontein.

CRM employs 2,800 people, including those working for contractors. As with many mines in South Africa as a whole and in the Rustenburg area itself, staff retention can be difficult for Eastplats, the contractors and for Atlas Copco. The mine works three shifts over an 11-day fortnight and has a detailed performance reporting system. At Maroelabult there are two declines, one housing the conveyor. Steady-state production was first achieved in mid-2007 and continues at a rate of 40,000 t/month ore, said Hartmann. Maroela and Zandfontein are mining a total of 36 panels with an area of 13,000 m2. The haulage contractor’s road route from the Maroela section ore loading facility to the Zandfontein concentrator is 16 km although the straight line distance is 9 km. Total output in the September quarter, the first of the 2008 financial year, was 330,000 mt ore, as compared with 160,000 mt in the equivalent period of FY2006, making Eastplats South Africa’s sixth largest platinum producer at 125,000 oz/y.

Focus on Zandfontein
Eastplats’ main objective at this time is to increase and stabilize production and productivity in the Zandfontein section. Albert Hartmann explained that the key steps taken to start increasing ore production from the section were:
• A new structural interpretation by Applied Geology Services and accurate mine modeling using Datamine’s Mine 2-4D and GSMI CADSMine software to build models from historical mining data.
• Creation of footwall drives to access the reef from below, in order to mine up the dip of the ore on an 18° slope; the previous system had accessed the ore panels from the top of the reef and tried to mine down dip at a 21° angle, which had, as reported by former BPIL owners Impala Platinum, proved very difficult. Development of the footwall drives and crosscuts to access the reef panels would be mechanized but the levels are connected by raises and winzes drilled manually. The lowest level will be 300 m below surface.
• Installation of a leaky feeder system that would provide excellent radio communication in the mine: this has been a big help in improving response times when staff and machines encounter problems, commented Hartmann.
• Utilization of a new fleet of Atlas Copco drilling rigs and standard size Scooptram LHDs and Minetrucks, backed up by a maintenance and repair contract with Atlas Copco Underground Rock Excavation. The mine ordered a single package comprising one each RB S1L and RB 281, and four RB 282 drilling rigs equipped with COP 1838 rock drills; one ST 1020 and six ST 1030 Scooptrams; and 15 Minetrucks—two MT 2000 and 13 MT 2010s.


Technicians discuss the work required on one of CRM’s Boomer drill rigs.
In addition, and partly in response to a labor dispute during 2006, CRM brought in three contractors in order to keep up the pace of progress. J.I.C. Mining Services and Mulefe Cheetah took over ore production by conventional methods and Murray & Roberts Cementation was awarded three separate mine infrastructure development contracts. The new Atlas Copco fleet is divided between production duties and Murray & Roberts Cementation’s development work. At present some low-profile trucks built in Johannesburg by Fermel Mining Equipment & Supplies are also being used for ore haulage but these rented machines will soon be withdrawn. The new system was introduced in November 2006 and by fourth quarter 2007 the development program had reached 3 Level. The strategy is to develop the presently unexploited down dip reserves as quickly as possible and to create operational flexibility, Hartmann explained.

There are four decline shafts in use, accessing the reef down dip, and a vertical shaft that was sunk in 1988 but has been little used since 1990 and has been flooded to 60 m below the collar. Decline shafts Nos. 1, 2 and 4 are vehicle declines and No. 3 houses the conveyor system that delivers most of the mined ore to surface. The first section of each decline is 6 x 5 m in section but the drives in the areas now being developed are 4.5 x 4.0 m. The declines are rock bolted, with mesh in high-activity areas. The vertical shaft is being refurbished and deepened by Murray & Roberts Cementation to provide service access and probably ore hoisting using 16-t skips.

The Production contractors use the hybrid mining method—with compressed air supplied by Atlas Copco units at the sides of the declines. The stopes are manually drilled for both blasting and bolting. The scraper system pulls ore from the central gulleys to transfer points, either ore passes which discharge the ore to the haulage level where it is collected by Scooptram and then trammed to a truck loading point, or box loaders dumping to the trucks directly. Eastplats intends to equip all the central gulleys with box loaders, releasing the Scooptrams for development work. The trucks haul to the belt conveyor loading station in decline shaft 3, which has a screen and hydraulic breaker. Truck journeys average three minutes and the present loading and haulage system requires three trucks working with each loader.

When operations restarted, CRM had a rather mixed fleet of trucks, including articulated dump trucks designed for surface use and some old and unreliable vehicles, said Hartmann. Some units were cheap to run, others very expensive and this was one reason why he opted to tender for new equipment, finally choosing the Atlas Copco machines and service package. The LHDs and trucks can work approximately 18 hours per day, averaging 340 hr/month on development duty and 400 hr/month on production work.

Progressing Development
For decline extension and other development work outside the stoped areas fully mechanized techniques can be employed. Presently, the six Atlas Copco drilling rigs at Zandfontein are drilling 700 development meters per month, using 38-mm or 42-mm holes. The target for each twoboom rig is 120 m/month. Electricity supply is 550V and the rigs are monitored on a percussion hours basis.

Murray & Roberts Cementation, which is South Africa’s leading contractor, was awarded a first contract with Crocodile River mine in June 2006 covering development of a new Decline 5 and both rehabilitation and extension of Decline 2 to 3 Level at Zandfontein. This work is scheduled for completion in November 2008. The 17-month design-and-build contract for redeveloping the vertical shaft was awarded in November 2006. The third contract involves sinking inclines to access ore reserves and two to feed the vertical shaft. Future decline work will include development of three inclines to 9 Level plus development on 3 Level.

Work on decline shaft 2 included rebuilding and extending the existing roadway, ventilation pipework and other services concurrent with normal development work. The contractor uses three of the two-boom Rocket Boomers and, since the rehab program reached 2 Level, has been driving a 4 x 4-m haulage eastward on this level to connect with decline shaft 3. The crew uses 4-m-long drill steels and blasts at the end of each shift. Mucking is with the LHDs and trucks. Concurrently Murray & Roberts Cementation is extending the decline shaft to 3 Level.

The vertical shaft, which is still in excellent condition but lacking some original equipment, was dewatered down to 2 Level before the contractor started work and holing into the shaft at this level has provided multi-blast conditions. At the time of E&MJ’s visit, the 550-m-deep shaft was being used for ventilation. The headgear A-frame was brought from Eastplats’ Kennedy’s Vale property some 300 km away and arrived in September 2007. The contract covers refurbishment and installation of this frame, supply of the headgear center tower, reinstallation of the main winder and sourcing of a rock winder. Shaft rehabilitation involved removal and modification of the stage, the installation of the kibble and stage winders: equipping started in CRM’s second (October-December 2007) FY2008 quarter. The shaft will be provided with a conveyor belt level, loading and water pumping and settling facilities. Scheduled for completion in May 2008, the shaft will initially be used for personnel and materials but by the end of 2008 should be hoisting 120,000 mt/month rock.

To treat increasing ore output Eastplats has also been making substantial investments in the concentrator, which was recently expanded to a capacity of 250,000 t/month while a chrome recovery circuit was due on-stream in December 2007. In addition, a new $2.28-million tailings retreatment plant at Zandfontein was commissioned earlier in 2007 and is intended to add 5,000 oz/y to Eastplats PGM output. The company is evaluating the possibility of restarting the smelter.

The first additional ore production will be from the Crocette section, 7 km from Zandfontein, while a feasibility study of the Kareespruit section is planned for 2008, with a nominal output target of 120,000 t/month, and CRM will start exploratory drilling at Maroelabult North. Portal construction at Crocette, which did not require any blasting, has been completed but excavation was awaiting the necessary mining license when E&MJ visited. The reef lies only 130 m from the portal so mine development can start not long after a license is granted and Eastplats has already ordered the necessary equipment from Atlas Copco. The immediate target is a steady 40,000 t/month, as at Maroelabult, and this will also be trucked by contractor to the concentrator at Zandfontein.

Improving Maintenance
Effective maintenance practices are playing a crucial part in Crocodile River’s progress, said Hartmann. Under the mobile equipment service contract, which started on September 1, 2006, Eastplats pays Atlas Copco a rate per hour that covers everything on the machines and includes a rebuild of the LHDs at 15,000 hours in addition to the full service schedule. Maintenance is scheduled on a daily basis and the mine engineer and mine captains call in the units required. The mine also has a rock drilling tools supply contract with Atlas Copco that is managed by the Atlas Copco branch at Rustenburg, with a container at Crocodile River. According to Mine Engineer Jerry Oosthuizen, Eastplats is a leader on performance- based variable rate drill steels contracts in South Africa.


ProMaint software helps Crocodile River mine’s Atlas
Copco maintenance and contract managers do their
jobs.
Reporting to François van Tonder, national contracts manager in Johannesburg, Atlas Copco’s contract manager at Crocodile River is Hennie Booysen. The contract with Eastplats is hours-based and is operated as a partnership in which, said Booysen, honesty maintains trust. He and his team of 36 people work in the mine’s main workshop building and the team comprises four groups: Services, headed by a foreman; Breakdowns, also led by a foreman; Stores, headed by a supervisor; and the administration team which works directly with Booysen to ensure smooth running of the contract. The two parties use Atlas Copco’s ProMaint package to store and utilize detailed hourly, shift, day, week, month and annual performance data provided by the equipment operators. The equipment database software is held on the mine’s computer system so the Eastplats Engineering department can access the reported information and various other mine staffers have passwords to access specified sections of the database.

The Services foreman has a team of four service technicians, four assemblers and a boilermaker. The bulk of planned service work on the fleet is done during the morning shift and the equipment then goes underground. The Breakdowns foreman has a permanent morning shift team and a breakdown mechanic, plus three shift breakdown teams, each of which comprises two service technicians, one assembler and one electrician. The Stores supervisor has a store man and assistant during the service shift and three shift foremen to supply the breakdown teams. The administration team is made up of the maintenance planner, data clerk–administration and data clerkplanning. Floors Foord, the Underground rock excavation (URE) area manager covering the Bushveld, provides product support from the Atlas Copco South Africa headquarters in Johannesburg.

The Atlas Copco maintenance planner uses ProMaint to work out the forward service requirements for each machine on the basis of the database information and Booysen, who is the end-user of ProMaint, can plan the maintenance schedules accordingly. He commented that he had helped outline generic service information for the ProMaint design team but had not used the system until he started working on the Crocodile River contract. It does yield a great deal of the information he needs for maintenance planning, he said.

Clearly, the operators must input data thoroughly for the whole system to function and equally the Atlas Copco staff must make the mine management aware of any problems they have with keeping the equipment running to plan. Hennie Booysen contacts Albert Hartmann at the morning shift change, second shift change and in the evening, as well as when any major breakdowns occur. Atlas Copco has fortnightly meetings with the mine’s Engineering team who also have their offices on the first floor of the workshop building and the Administration group produces a monthly report for the mine and for Atlas Copco in Johannesburg.

The Atlas Copco team at the mine holds many parts on site, with larger items such as engines held in Johannesburg. Most of the units have Cummins engines that typically run 8,000 – 10,000 hours between rebuilds. Any Cummins engine that fails is examined at the manufacturer’s facility in Johannesburg. Hartmann looked at the historical actual running costs for all the trucks used before and during the first 10 months of the service contract and found that those for the Minetrucks are significantly the lowest.

Another key element contributing to better production performance and cost reduction is the mine’s focus on roadway maintenance. Eastplats is using waste rock crushed to 50 mm by a contractor for the roadbeds and two graders and five skid-steers work 24 hours a day on maintaining the roadways to a standard that allows not only loaders and trucks but conventional 4WD utility vehicles to run without difficulty. Surplus aggregate is sold off mine. Tire management is contracted to Tyre Corp. and Eastplats has achieved a considerable increase in tyre life, for example from 300–400 hours previously to 1,500 hours on the Scooptrams and to 2,000 hours on the Minetrucks (although these averages are still low in comparison with the same vehicles operating in many other mines).

As featured in Womp 08 Vol 2 - www.womp-int.com