Kroondal a Flagship for Contract Mining
The Kroondal platinum group metal (PGM) mine, located 120km northwest of Johannesburg on the Western Limb of the Bushveld Complex, was Aquarius Platinum’s first operation.
It commenced production in 1999 and remains the company’s flagship project. It is also mining contractor Murray & Roberts Cementation’s flagship contract, with the group having mined Kroondal on behalf of Aquarius since the start.
That is likely to remain the case for the foreseeable future, with the life of the mine extended by the pool and share agreement with Anglo Platinum.
When Kroondal increased its production rate in 2000 by 66% a pool and share transaction that incorporated the Anglo Platinum reserves adjacent to Kroondal. This extended Kroondal’s life-of-mine to 2014.
The capital-intensive small-mine concept developed at Kroondal by Aquarius revolutionised the PGM mining sector in South Africa. This approach includes the use of key contractors, such as Murray & Roberts Cementation, MCC and Minopex, and a highly mechanised mining operation. Murray & Roberts Cementation’s responsibility ends on the surface pad where surface contractor MCC and plant operator Minopex take over.
A feature of Kroondal is its conveyor belt system onto which load haul dumpers (LHDs) tip the ore. The use of a belt system and trackless fleet means no scrapers or dump trucks and this helps keep Kroondal a relatively low cost producer with high productivity levels. Kroondal’s Central shaft alone has an estimated 42km of conveyor belting.
Kroondal’s orebody comprises two UG2 seams, the main and the leader seams, separated by a 700mm to 1.2m pyroxenite barren zone commonly known as the parting.
The main and leader seams are mined together with the parting and this gives Kroondal, now solely an underground mine, an average stoping width of about 1.8m. The cut-off at the top is on the hangingwall and there is about 20cm of overburden at the footwall. Blast control creates large waste rocks in the parting zone and a large proportion of these are removed underground to improve the economics of this wide reef operation. A Dense Media Separation (DMS) process in the concentrator plant removes further waste from the ore stream.
The biggest of the mine’s three decline shafts is the 230,000tpm central shaft where mining comprises mechanised bord and pillar with single boomer drill rigs and some hand held drilling sections. That is also true for Kroondal’s 160,000tpm eastern shaft. The central shaft extends to a vertical depth of 300m which translates to about 3km in actual shaft length, once the 12° dip of the orebody is taken into account.
The eastern shaft extends to a vertical depth of 270m and comprises a total length of about 2.6km, and the third shaft, named No 3 shaft, extends to a vertical depth of 220m and extends about 2.2km.
Braam Blom, Murray & Roberts Cementation general manager at Kroondal, says that in future the construction of vertical lift shafts will need to be considered due to the length of the decline shafts which become ineffective at depth.
In addition to Kroondal, Murray & Roberts Cementation undertakes contract mining at Aquarius Platinum’s nearby Marikana project. The Marikana shafts extend down about 100m to 120m. Both Kroondal and Marikana are managed by the same Murray & Roberts Cementation team headquartered at Kroondal.
The pillars at Kroondal’s Central shaft are 10m wide based on the support requirement, and will increase in size as the depth increases.
“Face redundancy is maintained to ensure sufficient flexibility and the amount of this redundancy is based on geological losses,” Blom says. “We need the flexibility to ensure that for every six panels available, two are being drilled and blasted, two are being cleaned and support is being set up in the remaining two in each shift cycle. We plan at 50% redundancy to manage this mining cycle.”
Overall at Kroondal there is a 62% face redundancy, with Marikana being 35% face redundancy, as it is still building up to where it can be called a steady state operation.
Like Kroondal, the Marikana mine consists of three shafts and will reach steady state in the middle of 2009. The main shaft at Marikana is the No 4 shaft with production of 120,000tpm, while the No 1 and No 2 shafts are, due to the geological constraints of the orebody, designed to produce 20,000tpm and 20,000tpm respectively. This adds up to the 160,000tpm operation that is Marikana.
The planned head grade for Kroondal is 2.8g/t of PGMs and the face grade is about 2.7g/t. At Marikana, which occasionally requires redevelopment off reef to align with the UG2 seams, the face grade is about 2.6g/t.
“Murray & Roberts Cementation’s contract for mining Kroondal and Marikana is based on a rate per unit which comprises of ledging, stoping and development.” Blom says. “The strategy to employ contractors by Aquarius was used to cater for the short life-of-mine of the initial orebody, and was subsequently extended by additional lease areas being made available. For us it is a low margin high volume contract.”
Aquarius gains is the elimination of overhead cost utilizing a small management team to co-ordinate and manage the operation and have a degree of confidence that its production levels will be in line or better than industry standards.
Labour accounts for 55% of the input costs and wages have shown double digit escalation. The next biggest cost is plant related, including maintenance of the mining equipment fleet, and consumables such as fuel and tyres. Overheads have increased to keep up with market related remuneration and incentives and the safety related interventions demands put on the system.
Murray & Roberts Cementation is undertaking a comprehensive safety programme at Kroondal and Marikana. Blom says that the Safety and business culture and safety campaigns, embodied in the words ‘doing the job right the first time’ comprises three distinct focal points. “One is the focus on the safety of the person or individual,and involves the education, training and development or ability of the employee The second focal point is the workplace where we ensure the proper systems and tools are in place. The third is a focus on behavioural changes to ensure that a culture of ‘no at risk behaviour’ and ‘accountability’ becomes entrenched.”
The impact to date of this campaign was a reduction of the lost time injury rate from 7.2 a year ago to 2.9 in November last year. “There is a major improvement year on year and indicates an overall sustainable downward trend trend in the safety graphs.Our aim is to achieve the Murray & Roberts Cementation safety target of 2.5LTI per million hours rate before June 2008 and indication are that we might do so by March 08 should we continue on this positive trend. This will require dedication and commitment by the Kroondal and Marikana team and all stakeholders. Both the unions, NUM and Solidarity is playing a major role in the implementation of our safety culture and is supporting the current drive to zero harm.
Kroondal has its own centre where it not only does compulsory induction programmes, but does skills training such LHD driver training, Dover testing, Competancy A and B training and first aid training. Technology utilized in training for computerized skills training, a planned LHD simulator to be in place by March 08 to have a safe and cost effective alternative to initial underground training, but the underground hands on training will continue once the individual has reached a degree of competency to do so. The remote support of the workings has been brought in such as the Minova Autorock roof support devices to create a safe working environment when installing roof support.
Blom also sees mining costs escalating over the next few years because of the tight labour market and mining boom experienced due to a high platinum and gold commodity prices.
The shortage of critical skills such as LHD drivers, rock drill operators, drill rig operators and engineering artisans will be the biggest challenge to the mining fraternity and it is crucial that all the mining houses, contractors and training facilities do their bit to ensure that these critical shortages are addressed through training and development of employees.
The effect of the increase in the number of mining projects is a high turnover of labour across the industry. Turnover among the workforce including sick leave is about 12% to 14%, which is typical across the mining industry. And while managing turnover, which reaches 2% to 3% monthly, the contractor must maintain output and keep overhead costs under control if it is to avoid losses.
“Aquarius has representation on all decision making teams,” Blom says. “The relationship with the client is very important; for the operation to work a supportive environment is required to implement all the policies.” Aquarius has a small highly skilled management team.
Murray & Roberts Cementation manages its risk through ownership of its fleet which at Kroondal and Marikana and comprises about 120 LHDs and 17 drill rigs. “We do most of the re-built programs of the LHD fleet and repair in-house and have already successfully completed 45 units this financial year alone,” Blom says. The result is a total fleet availability of 85% and this is planned to increase to an effective 93% once the planned maintenance and rebuilt program is taken into account.
About four years ago the decision was taken to mechanise the drilling at the Kroondal operations, with hand-held drilling still making up about 50% of total mining. Today hand-held drilling are used where panel conditions are not conducive for mechanised drilling, such as re-establishment and reduced faces lengths.
Hand-held teams can also be brought in on short notice to mine extra panels to manage production requirements. Hand-held drilling also is used for parts of the orebody where it dip increases to 18°, as it does at Marikana, as opposed to a more typical 9° to 12° for Kroondal.
In addition to the Kroondal/Marikana contract Murray & Roberts Cementation has two other mining contracts, these being at Blue Ridge and Dwarsrivier.
This press release is credited to Mining Review Africa.